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Linear approximation

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55105812
A differentiable function satisfies \(f(2)=7\) and \(f'(2)=-3\). Use the linear approximation at \(x=2\) to estimate \(f(2.04)\).

Hints

- A linear approximation uses the known function value and derivative at the center point. - Measure how far the target input is from the center. - Apply the local linear change to the known function value.

Solution

1. The linear approximation at \(x=2\) is \(L(x)=f(2)+f'(2)(x-2)\). 2. Thus, \(L(x)=7-3(x-2)\). 3. Evaluate at \(x=2.04\): \(L(2.04)=7-3(0.04)=6.88\). 4. Therefore, \(f(2.04)\approx6.88\).

Answer

\(f(2.04)\approx6.88\)
52646912
Let \(f(x)=3\sin x+2\). 1. Find the slope of the tangent line at \(x=\frac{\pi}{3}\). 2. Find every input in \([0, 2\pi]\) where the tangent line is parallel to \(y=1.5x-4\).

Hints

- The derivative gives the tangent slope. - Parallel lines have equal slopes. - Set the derivative equal to \(1.5\). - Use the unit circle to solve the cosine equation.

Solution

1. Differentiate: \(f'(x)=3\cos x\). Thus, \(f'\left(\frac{\pi}{3}\right)=3\cdot\frac{1}{2}=1.5\). 2. A parallel tangent must have slope \(1.5\), so \(3\cos x=1.5\). Therefore, \(\cos x=\frac{1}{2}\). In \([0, 2\pi]\), the solutions are \(x=\frac{\pi}{3}\) and \(x=\frac{5\pi}{3}\).

Answer

1. The slope is \(1.5\). 2. \(x=\frac{\pi}{3}\) and \(x=\frac{5\pi}{3}\)
52767712
Let \(f(x)=\ln x+3\), where \(x>0\). a) Describe how the graph is obtained from the graph of \(y=\ln x\). b) Use the logarithm derivative rule to find \(f'(x)\). c) Find an equation of the tangent line at \(x=1\).

Hints

- A constant added outside a function creates a vertical shift. - Differentiate the logarithm and the added constant separately. - For the tangent line, combine the function value and derivative value at \(x=1\).

Solution

1. Adding \(3\) shifts the graph of \(y=\ln x\) upward by \(3\) units. 2. The derivative of \(\ln x\) is \(\frac1x\), and the constant has derivative \(0\), so \(f'(x)=\frac1x\). 3. At \(x=1\), \(f(1)=3\) and \(f'(1)=1\). The tangent line is \(y-3=x-1\), or \(y=x+2\).

Answer

a) Shift the graph of \(y=\ln x\) up \(3\) units. b) \(f'(x)=\frac1x\) c) \(y=x+2\)
52991412
Let \(g(x)=x\cdot 3^x\). a) Find \(g'(x)\). b) Find the equation of the tangent line to the graph at the origin.

Hints

- Use the product rule. - Recall the derivative of \(3^x\). - Evaluate the derivative at \(x=0\). - Use the origin and the slope to write the tangent line.

Solution

1. Use the product rule with \(u(x)=x\) and \(v(x)=3^x\): \(g'(x)=3^x+x(\ln 3)3^x\) \(=3^x(1+x\ln 3)\). 2. Since \(g(0)=0\), the graph passes through the origin. The tangent slope is \(g'(0)=3^0(1+0\ln 3)=1\). Therefore, the tangent line is \(y=x\).

Answer

a) \(g'(x)=3^x(1+x\ln 3)\) b) \(y=x\)
55105912
Let \(f(x)=\sqrt[3]{x}\). Use the linearization of \(f\) at \(x=8\) to approximate \(\sqrt[3]{8.3}\).

Hints

- Choose the nearby input where the cube root is easy to evaluate exactly. - Build the tangent-line approximation from the function value and derivative at that input. - Substitute the target input into the linearization, not into a new derivative calculation.

Solution

1. \(f(8)=2\), and \(f'(x)=\frac{1}{3x^{2/3}}\), so \(f'(8)=\frac{1}{12}\). 2. The linearization is \(L(x)=2+\frac{1}{12}(x-8)\). 3. Therefore, \(\sqrt[3]{8.3}\approx L(8.3)=2+\frac{0.3}{12}=2.025\).

Answer

\(\sqrt[3]{8.3}\approx2.025\)
55106012
A metal cube has side length \(10.00\,\text{cm}\). Thermal expansion increases the side length by \(0.02\,\text{cm}\). Use a linear approximation to estimate the increase in the cube's volume.

Hints

- Treat volume as a function of the cube's side length. - A small input change can be estimated using the derivative at the original measurement. - The requested change is a volume, so check the units of the estimate.

Solution

1. The volume as a function of side length is \(V(s)=s^3\), so \(V'(s)=3s^2\). 2. Near \(s=10\), a small change \(\Delta s\) produces \(\Delta V\approx V'(10)\Delta s\). 3. With \(\Delta s=0.02\), \(\Delta V\approx3(10)^2(0.02)=6\,\text{cm}^3\).

Answer

The volume increases by approximately \(6\,\text{cm}^3\).
55586912
Let \(f(x)=e^x\). a) Find the linearization \(L(x)\) at \(a=0\). b) Use it to approximate \(e^{0.04}\).

Hints

- Evaluate both the function and its derivative at the center \(a=0\). - Use \(L(x)=f(a)+f'(a)(x-a)\). - Substitute the nearby input into the linearization, not back into the original exponential function.

Solution

1. \(f(0)=1\) and \(f'(x)=e^x\), so \(f'(0)=1\). 2. Therefore, \(L(x)=f(0)+f'(0)(x-0)=1+x\). 3. \(e^{0.04}\approx L(0.04)=1.04\).

Answer

a) \(L(x)=1+x\) b) \(e^{0.04}\approx1.04\)
52557312
Let \(f(x)=\cos x\). Find all points on the graph where the tangent line is a) parallel to \(y=-\frac{1}{2}x+5\), b) perpendicular to \(y=x\).

Hints

- The derivative gives the tangent slope. - Parallel lines have equal slopes; perpendicular nonvertical lines have slopes whose product is \(-1\). - Use unit-circle values and periodicity. - Substitute each x-coordinate into the original function.

Solution

1. The derivative is \(f'(x)=-\sin x\). 2. In part a, a parallel tangent must have slope \(-\frac{1}{2}\). Thus, \(-\sin x=-\frac{1}{2}\), so \(\sin x=\frac{1}{2}\). The solutions are \(x=\frac{\pi}{6}+2k\pi\) or \(x=\frac{5\pi}{6}+2k\pi\), where \(k\in\mathbb{Z}\). The corresponding y-coordinates are \(\frac{\sqrt{3}}{2}\) and \(-\frac{\sqrt{3}}{2}\). 3. In part b, a line perpendicular to \(y=x\) has slope \(-1\). Thus, \(-\sin x=-1\), so \(\sin x=1\). Therefore, \(x=\frac{\pi}{2}+2k\pi\), and the y-coordinate is \(0\).

Answer

a) \(\left(\frac{\pi}{6}+2k\pi, \frac{\sqrt{3}}{2}\right)\) and \(\left(\frac{5\pi}{6}+2k\pi, -\frac{\sqrt{3}}{2}\right)\), where \(k\in\mathbb{Z}\) b) \(\left(\frac{\pi}{2}+2k\pi, 0\right)\), where \(k\in\mathbb{Z}\)
52557412
The graph of \(g(x)=2\sin x\) has slope \(\sqrt{2}\) at infinitely many points. Find the coordinates of all such points.

Hints

- Differentiate using the constant multiple rule. - Set the derivative equal to the given slope. - Use the unit circle and periodicity to solve the trigonometric equation. - Substitute the inputs into the original function for the y-coordinates.

Solution

1. Differentiate: \(g'(x)=2\cos x\). 2. Set the derivative equal to the required slope: \(2\cos x=\sqrt{2}\), so \(\cos x=\frac{\sqrt{2}}{2}\). Therefore, \(x=\frac{\pi}{4}+2k\pi\) or \(x=-\frac{\pi}{4}+2k\pi\), where \(k\in\mathbb{Z}\). 3. Evaluate \(g\): \(g\left(\frac{\pi}{4}\right)=\sqrt{2}\) and \(g\left(-\frac{\pi}{4}\right)=-\sqrt{2}\).

Answer

\(\left(\frac{\pi}{4}+2k\pi, \sqrt{2}\right)\) and \(\left(-\frac{\pi}{4}+2k\pi, -\sqrt{2}\right)\), where \(k\in\mathbb{Z}\)
52557512
Find the equation of the tangent line to the graph of \(f(x)=\sin x\) at \(P=\left(\frac{2\pi}{3}, \frac{\sqrt{3}}{2}\right)\).

Hints

- The derivative gives the tangent slope. - Use the exact cosine value at \(\frac{2\pi}{3}\). - Write the line in point-slope form. - Keep all angle measures in radians.

Solution

1. Differentiate: \(f'(x)=\cos x\). 2. The tangent slope is \(m=f'\left(\frac{2\pi}{3}\right)=\cos\left(\frac{2\pi}{3}\right)=-\frac{1}{2}\). 3. Use point-slope form: \(y-\frac{\sqrt{3}}{2}=-\frac{1}{2}\left(x-\frac{2\pi}{3}\right)\). Simplifying gives \(y=-\frac{1}{2}x+\frac{\pi}{3}+\frac{\sqrt{3}}{2}\).

Answer

\(y=-\frac{1}{2}x+\frac{\pi}{3}+\frac{\sqrt{3}}{2}\)
52557612
Let \(g(x)=2\cos x\). Find the equation of the tangent line to the graph at \(x_0=\frac{\pi}{6}\).

Hints

- Evaluate the function to find the point of tangency. - Differentiate using the constant multiple rule. - Use the exact sine and cosine values at \(\frac{\pi}{6}\). - Write the tangent line in point-slope form.

Solution

1. Find the point of tangency: \(g\left(\frac{\pi}{6}\right)=2\cos\left(\frac{\pi}{6}\right)=\sqrt{3}\). 2. Differentiate: \(g'(x)=-2\sin x\). The tangent slope is \(g'\left(\frac{\pi}{6}\right)=-2\cdot\frac{1}{2}=-1\). 3. Use point-slope form: \(y-\sqrt{3}=-\left(x-\frac{\pi}{6}\right)\). Therefore, \(y=-x+\frac{\pi}{6}+\sqrt{3}\).

Answer

\(y=-x+\frac{\pi}{6}+\sqrt{3}\)
52560712
Let \(f(x)=\cos x-2\sin x\). Find the equation of the tangent line at \(P=\left(\frac{\pi}{2}, f\left(\frac{\pi}{2}\right)\right)\). Also find the angle of inclination of the tangent line.

Hints

- Evaluate the function and derivative at the given input. - Use point-slope form for the tangent line. - The derivative value is the tangent slope. - Choose the angle of inclination in the interval \([0^\circ, 180^\circ)\).

Solution

1. Evaluate the function: \(f\left(\frac{\pi}{2}\right)=0-2=-2\). Thus, the point is \(\left(\frac{\pi}{2}, -2\right)\). 2. Differentiate: \(f'(x)=-\sin x-2\cos x\). The tangent slope is \(f'\left(\frac{\pi}{2}\right)=-1\). 3. Use point-slope form: \(y+2=-\left(x-\frac{\pi}{2}\right)\). Therefore, \(y=-x+\frac{\pi}{2}-2\). 4. The angle of inclination is measured counterclockwise from the positive x-axis and satisfies \(\tan\alpha=-1\). Thus, \(\alpha=135^\circ\).

Answer

Tangent line: \(y=-x+\frac{\pi}{2}-2\) Angle of inclination: \(135^\circ\)
52560812
Let \(f(x)=2\sin(2x)+\cos x\). Find the equation of the tangent line at \(x=\frac{\pi}{3}\). Also find the tangent line’s angle of inclination to the nearest hundredth of a degree.

Hints

- Use the chain rule when differentiating \(\sin(2x)\). - Evaluate both the function and derivative at the given input. - Use point-slope form for the tangent line. - For a negative slope, choose the inclination angle in the second quadrant.

Solution

1. Find the point of tangency: \(f\left(\frac{\pi}{3}\right)=2\sin\left(\frac{2\pi}{3}\right)+\cos\left(\frac{\pi}{3}\right)=\sqrt{3}+\frac{1}{2}\). 2. Differentiate using the chain rule: \(f'(x)=4\cos(2x)-\sin x\). The tangent slope is \(m=f'\left(\frac{\pi}{3}\right)=-2-\frac{\sqrt{3}}{2}\). 3. Use point-slope form: \(y-\left(\sqrt{3}+\frac{1}{2}\right)=\left(-2-\frac{\sqrt{3}}{2}\right)\left(x-\frac{\pi}{3}\right)\). Equivalently, \(y=\left(-2-\frac{\sqrt{3}}{2}\right)x+\frac{2\pi}{3}+\frac{\pi\sqrt{3}}{6}+\sqrt{3}+\frac{1}{2}\). 4. The angle of inclination \(\alpha\in[0^\circ, 180^\circ)\) satisfies \(\tan\alpha=m\). Since the slope is negative, \(\alpha\approx 109.23^\circ\).

Answer

Tangent line: \(y-\left(\sqrt{3}+\frac{1}{2}\right)=\left(-2-\frac{\sqrt{3}}{2}\right)\left(x-\frac{\pi}{3}\right)\) Angle of inclination: \(\alpha\approx 109.23^\circ\)
52560912
Let \(f(x)=2\sin x\) and \(g(x)=2\cos x\). a) Find the intersection point \(S\) of the graphs on \([0,\pi]\). b) Find the angles of inclination \(\alpha\) and \(\beta\) of the tangent lines to the graphs of \(f\) and \(g\), respectively, at \(S\), to the nearest hundredth of a degree. c) Find the smaller angle \(\gamma\) at which the graphs intersect at \(S\), to the nearest hundredth of a degree.

Hints

- Set the two function values equal to find the intersection. - Use the sine and cosine derivative formulas for the tangent slopes. - Convert each slope to its inclination angle in \([0^\circ,180^\circ)\). - Use the smaller difference of the inclination angles and the requested precision.

Solution

1. At an intersection, \(2\sin x=2\cos x\). On \([0,\pi]\), this gives \(x=\frac{\pi}{4}\), with y-coordinate \(\sqrt{2}\). Thus, \(S=\left(\frac{\pi}{4},\sqrt{2}\right)\). 2. The derivatives are \(f'(x)=2\cos x\) and \(g'(x)=-2\sin x\). At \(S\), the slopes are \(\sqrt{2}\) and \(-\sqrt{2}\). 3. Therefore, \(\alpha=\arctan(\sqrt{2})\approx54.74^\circ\) and \(\beta=180^\circ-54.74^\circ\approx125.26^\circ\). 4. The smaller intersection angle is \(\gamma=\beta-\alpha\approx70.53^\circ\).

Answer

a) \(S=\left(\frac{\pi}{4},\sqrt{2}\right)\) b) \(\alpha\approx54.74^\circ\); \(\beta\approx125.26^\circ\) c) \(\gamma\approx70.53^\circ\)
52561512
Let \(f(x)=\sin x+\cos x\). Find the equation of the tangent line at \(x_0=\frac{\pi}{2}\). Also find its angle of inclination.

Hints

- Evaluate the function and derivative at the given input. - Use point-slope form. - Relate the derivative value to the tangent slope. - Give the inclination angle in \([0^\circ, 180^\circ)\).

Solution

1. The point of tangency is \(\left(\frac{\pi}{2}, 1\right)\). 2. Differentiate: \(f'(x)=\cos x-\sin x\). The slope at \(x=\frac{\pi}{2}\) is \(-1\). 3. Use point-slope form: \(y-1=-\left(x-\frac{\pi}{2}\right)\). Therefore, \(y=-x+\frac{\pi}{2}+1\). 4. Since the slope is \(-1\), the angle of inclination is \(135^\circ\).

Answer

Tangent line: \(y=-x+\frac{\pi}{2}+1\) Angle of inclination: \(135^\circ\)
52561612
Let \(g(x)=2\cos x+1\). Find the equation of the tangent line at \(P=\left(\frac{2\pi}{3}, g\left(\frac{2\pi}{3}\right)\right)\). Then find its angle of inclination.

Hints

- Evaluate the function to find the point. - Differentiate cosine and keep the constant factor. - Use point-slope form for the tangent line. - A slope of \(-\sqrt{3}\) has an inclination angle in the second quadrant.

Solution

1. Evaluate the function: \(g\left(\frac{2\pi}{3}\right)=2\cdot\left(-\frac{1}{2}\right)+1=0\). Thus, the point is \(\left(\frac{2\pi}{3}, 0\right)\). 2. Differentiate: \(g'(x)=-2\sin x\). The tangent slope is \(g'\left(\frac{2\pi}{3}\right)=-\sqrt{3}\). 3. Use point-slope form: \(y=-\sqrt{3}\left(x-\frac{2\pi}{3}\right)\). Therefore, \(y=-\sqrt{3}x+\frac{2\pi\sqrt{3}}{3}\). 4. The standard angle of inclination in \([0^\circ, 180^\circ)\) is \(120^\circ\).

Answer

Tangent line: \(y=-\sqrt{3}x+\frac{2\pi\sqrt{3}}{3}\) Angle of inclination: \(120^\circ\)
52562712
Let \(f(x)=2\cos x+x\). Find equations for the tangent line and the normal line to the graph at \(P=(\pi, f(\pi))\).

Hints

- Evaluate the function at the given input. - Use the derivative to find the tangent slope. - The normal slope is the negative reciprocal of the tangent slope. - Write both lines in point-slope form.

Solution

1. Find the point: \(f(\pi)=2\cos\pi+\pi=\pi-2\). Thus, \(P=(\pi, \pi-2)\). 2. Differentiate: \(f'(x)=-2\sin x+1\). The tangent slope is \(f'(\pi)=1\). Therefore, the tangent line is \(y-(\pi-2)=x-\pi\), or \(y=x-2\). 3. The normal slope is \(-1\). Thus, \(y-(\pi-2)=-(x-\pi)\), or \(y=-x+2\pi-2\).

Answer

Tangent line: \(y=x-2\) Normal line: \(y=-x+2\pi-2\)
52562812
Let \(f(x)=\sin x-\cos x\). Find equations for the tangent line and the normal line to the graph at \(P=\left(\frac{\pi}{2}, f\left(\frac{\pi}{2}\right)\right)\).

Hints

- Evaluate the function to locate the point. - Differentiate sine and cosine carefully. - Use the derivative value as the tangent slope. - Use the negative reciprocal for the normal slope.

Solution

1. Evaluate the function: \(f\left(\frac{\pi}{2}\right)=1\). Thus, the point is \(\left(\frac{\pi}{2}, 1\right)\). 2. Differentiate: \(f'(x)=\cos x+\sin x\). The tangent slope is \(f'\left(\frac{\pi}{2}\right)=1\). Therefore, the tangent line is \(y-1=x-\frac{\pi}{2}\), or \(y=x-\frac{\pi}{2}+1\). 3. The normal slope is \(-1\). Thus, \(y-1=-\left(x-\frac{\pi}{2}\right)\), or \(y=-x+\frac{\pi}{2}+1\).

Answer

Tangent line: \(y=x-\frac{\pi}{2}+1\) Normal line: \(y=-x+\frac{\pi}{2}+1\)
52595912
Let \(f(x)=\sin x(1+\cos x)\). Find equations for the tangent line and the normal line to the graph at \(x_0=\frac{\pi}{2}\).

Hints

- Evaluate the function at the given input. - Use the product rule to find the derivative. - Simplify with a double-angle identity if helpful. - Use negative reciprocal slopes for tangent and normal lines.

Solution

1. Evaluate the function: \(f\left(\frac{\pi}{2}\right)=1\). Thus, the point is \(\left(\frac{\pi}{2}, 1\right)\). 2. Differentiate using the product rule: \(f'(x)=\cos x(1+\cos x)-\sin^2x\). Using \(\cos^2x-\sin^2x=\cos(2x)\), \(f'(x)=\cos x+\cos(2x)\). Therefore, \(f'\left(\frac{\pi}{2}\right)=-1\). 3. The tangent line is \(y-1=-\left(x-\frac{\pi}{2}\right)\), or \(y=-x+\frac{\pi}{2}+1\). 4. The normal slope is \(1\), so the normal line is \(y-1=x-\frac{\pi}{2}\), or \(y=x-\frac{\pi}{2}+1\).

Answer

Tangent line: \(y=-x+\frac{\pi}{2}+1\) Normal line: \(y=x-\frac{\pi}{2}+1\)
52596012
Let \(f(x)=\cos^2x-\sin x\). Find equations for the tangent line and the normal line to the graph at \(P=(\pi, f(\pi))\).

Hints

- Evaluate the function at \(\pi\). - Use the chain rule for \(\cos^2x\). - The derivative value is the tangent slope. - Use the negative reciprocal for the normal slope.

Solution

1. Evaluate the function: \(f(\pi)=\cos^2\pi-\sin\pi=1\). Thus, \(P=(\pi, 1)\). 2. Differentiate using the chain rule: \(f'(x)=2\cos x(-\sin x)-\cos x\) \(=-\sin(2x)-\cos x\). Therefore, \(f'(\pi)=1\). 3. The tangent line is \(y-1=x-\pi\), or \(y=x-\pi+1\). 4. The normal slope is \(-1\), so the normal line is \(y-1=-(x-\pi)\), or \(y=-x+\pi+1\).

Answer

Tangent line: \(y=x-\pi+1\) Normal line: \(y=-x+\pi+1\)
52608012
Let \(f(x)=10e^x+x^2\). Find the equation of the tangent line to the graph of \(f\) at \((-1, f(-1))\). Give the coefficients exactly. Then find the tangent line’s angle of inclination to the nearest tenth of a degree.

Hints

- Find both \(f(-1)\) and \(f'(-1)\). - Use point-slope form for the tangent line. - Keep \(e\) symbolic in the exact equation. - Use the inverse tangent of the slope to find the angle.

Solution

1. Find the point of tangency: \(f(-1)=10e^{-1}+1=\frac{10}{e}+1\). 2. Differentiate: \(f'(x)=10e^x+2x\). The slope at \(x=-1\) is \(m=f'(-1)=\frac{10}{e}-2\). 3. Use point-slope form: \(y-\left(\frac{10}{e}+1\right)=\left(\frac{10}{e}-2\right)(x+1)\). Simplifying gives \(y=\left(\frac{10}{e}-2\right)x+\frac{20}{e}-1\). 4. The angle of inclination satisfies \(\tan\theta=m\). Therefore, \(\theta=\arctan\left(\frac{10}{e}-2\right)\approx 59.2^\circ\).

Answer

Tangent line: \(y=\left(\frac{10}{e}-2\right)x+\frac{20}{e}-1\) Angle of inclination: \(\theta\approx 59.2^\circ\)
52609512
Let \(f(x)=e^{2x}+e^x\). Find equations for the tangent line \(t\) and the normal line \(n\) to the graph of \(f\) at \((0, f(0))\).

Hints

- Evaluate the function to find the point of tangency. - Differentiate using the chain rule. - Use the derivative value as the tangent slope. - The normal slope is the negative reciprocal of the tangent slope.

Solution

1. Find the point: \(f(0)=e^0+e^0=2\), so the point is \((0, 2)\). 2. Differentiate using the chain rule: \(f'(x)=2e^{2x}+e^x\). Thus, the tangent slope is \(m_t=f'(0)=2+1=3\). The tangent line is \(t:y-2=3(x-0)\), or \(t:y=3x+2\). 3. The normal slope is the negative reciprocal: \(m_n=-\frac{1}{3}\). Therefore, \(n:y-2=-\frac{1}{3}(x-0)\), or \(n:y=-\frac{1}{3}x+2\).

Answer

\(t:y=3x+2\) \(n:y=-\frac{1}{3}x+2\)
52609612
Let \(f(x)=(x-2)e^x\). Find equations for the tangent line and the normal line to the graph of \(f\) at \((0, f(0))\).

Hints

- Use the product rule to find the derivative. - Evaluate the function and derivative at \(x=0\). - Write the tangent line in point-slope form. - Use the negative reciprocal for the normal slope.

Solution

1. Find the point: \(f(0)=(-2)e^0=-2\), so the point is \((0, -2)\). 2. Differentiate using the product rule: \(f'(x)=e^x+(x-2)e^x=(x-1)e^x\). Thus, the tangent slope is \(m_t=f'(0)=-1\). The tangent line is \(y+2=-1(x-0)\), or \(y=-x-2\). 3. The normal slope is \(m_n=-\frac{1}{m_t}=1\). Therefore, the normal line is \(y+2=x\), or \(y=x-2\).

Answer

Tangent line: \(y=-x-2\) Normal line: \(y=x-2\)
52756612
Ignoring air resistance, the impact speed \(v\), in meters per second, after falling from a height \(h\), in meters, is modeled by \(v(h)=\sqrt{19.62h}\). a) Find the linearization \(L(h)\) of \(v\) at \(h_0=20\). b) Use \(L\) to approximate the impact speed from a height of \(21\,\text{m}\). c) Compare the approximation with the exact model value \(v(21)\), and find the absolute error.

Hints

- Use the linearization formula centered at \(h_0=20\). - A linear approximation replaces a nearby function value with the corresponding tangent-line value. - Find absolute error by taking the absolute value of the difference between the approximation and the exact model value.

Solution

1. At \(h=20\), \(v(20)=\sqrt{392.4}\approx19.809\). 2. Differentiate: \(v'(h)=\frac{9.81}{\sqrt{19.62h}}\), so \(v'(20)\approx0.495\). 3. The linearization is \(L(h)\approx19.809+0.495(h-20)\). 4. \(L(21)\approx19.809+0.495=20.304\,\text{m/s}\). 5. The exact model value is \(v(21)=\sqrt{412.02}\approx20.298\,\text{m/s}\). The absolute error is \(|20.304-20.298|\approx0.006\,\text{m/s}\).

Answer

a) \(L(h)\approx19.809+0.495(h-20)\) b) \(L(21)\approx20.304\,\text{m/s}\) c) \(v(21)\approx20.298\,\text{m/s}\); absolute error \(\approx0.006\,\text{m/s}\)
52759912
Let \(f(x)=\ln x\), where \(x>0\). a) Find an equation of the tangent line to the graph of \(f\) at \(x_0=e^2\). b) A tangent line to the graph passes through the origin. Find the point of tangency and the tangent-line equation. c) Another tangent touches the graph at \(x_1=\sqrt{e}\). Find the x-intercept of this tangent line.

Hints

- Write the tangent line at a general input \(u\). - A line through the origin has y-intercept \(0\). - The tangent slope is the derivative value at the point of tangency. - Use logarithm properties for powers of \(e\).

Solution

1. Differentiate: \(f'(x)=\frac{1}{x}\). 2. At \(x_0=e^2\), \(f(e^2)=2\) and \(f'(e^2)=\frac{1}{e^2}\). Therefore, \(y=\frac{1}{e^2}(x-e^2)+2=\frac{x}{e^2}+1\). 3. The tangent line at a general input \(u>0\) is \(y=\frac{1}{u}(x-u)+\ln u=\frac{x}{u}+\ln u-1\). For this line to pass through the origin, \(\ln u-1=0\), so \(u=e\). The point of tangency is \((e, 1)\), and the tangent line is \(y=\frac{x}{e}\). 4. At \(x_1=\sqrt{e}\), the tangent line is \(y=\frac{x}{\sqrt{e}}-\frac{1}{2}\). Setting \(y=0\) gives the x-intercept \(x=\frac{\sqrt{e}}{2}\).

Answer

a) \(y=\frac{x}{e^2}+1\) b) Point of tangency: \((e, 1)\); tangent line: \(y=\frac{x}{e}\) c) x-intercept: \(x=\frac{\sqrt{e}}{2}\)
52760012
Let \(f(x)=\ln x\). a) Find the tangent line to the graph of \(f\) that is parallel to \(y=x\). b) A tangent line to the graph passes through \(A(0, -2)\). Find its equation. c) Show that the tangent line at \(x=u\) intersects the y-axis at \((0, \ln u-1)\). Then find \(u\) when this y-intercept is \(3\).

Hints

- Parallel lines have equal slopes. - Write the tangent line at a general input \(u\). - A point on the y-axis determines the tangent’s y-intercept. - Set \(x=0\) in the general tangent equation.

Solution

1. A line parallel to \(y=x\) has slope \(1\). Since \(f'(x)=\frac{1}{x}\), solve \(\frac{1}{x}=1\), giving \(x=1\). Since \(f(1)=0\), the tangent line is \(y=x-1\). 2. The tangent line at a general input \(u>0\) is \(y=\frac{x}{u}+\ln u-1\). Passing through \((0, -2)\) requires \(\ln u-1=-2\), so \(u=e^{-1}\). The slope is \(1/u=e\), giving \(y=ex-2\). 3. From the general tangent equation, setting \(x=0\) gives \(y=\ln u-1\), so the y-intercept is \((0, \ln u-1)\). For an intercept of \(3\), \(\ln u-1=3\), so \(u=e^4\).

Answer

a) \(y=x-1\) b) \(y=ex-2\) c) The y-intercept is \((0, \ln u-1)\), and \(u=e^4\) when the intercept is \(3\).
52761412
Let \(k(x)=\ln((2x-4)^2)\) on its maximal domain. a) Find the domain. b) Find an equation of the tangent line to the graph at \(x=1\).

Hints

- Find where the squared expression equals zero. - Apply the chain rule carefully. - A tangent line requires a point and a slope. - Evaluate both the function and derivative at \(x=1\).

Solution

1. The logarithm’s argument is zero only when \(2x-4=0\), so \(x=2\). It is positive for every other real input. Therefore, \(D_k=\mathbb{R}\setminus\{2\}\). 2. Differentiate using the chain rule: \(k'(x)=\frac{4(2x-4)}{(2x-4)^2}=\frac{2}{x-2}\). At \(x=1\), \(k(1)=\ln4\) and \(k'(1)=-2\). Thus, the tangent line is \(y=-2(x-1)+\ln4=-2x+2+\ln4\).

Answer

a) \(D_k=\mathbb{R}\setminus\{2\}\) b) \(y=-2x+2+\ln4\)
52765112
Let \(f(x)=\ln(4-x)\), where \(x<4\). Find the zero of \(f\) and an equation of the tangent line at \(x=3\).

Hints

- Use the fact that \(\ln1=0\). - Apply the chain rule to find the derivative. - A tangent line requires a point and a slope. - Use point-slope form.

Solution

1. To find the zero, solve \(\ln(4-x)=0\). Thus, \(4-x=1\), so \(x=3\). 2. Differentiate: \(f'(x)=-\frac{1}{4-x}=\frac{1}{x-4}\). At \(x=3\), \(f(3)=0\) and \(f'(3)=-1\). Therefore, the tangent line is \(y=-(x-3)=-x+3\).

Answer

Zero: \(x=3\) Tangent line: \(y=-x+3\)
52767812
Let \(g(x)=1-2\ln x\), where \(x>0\). a) Describe the transformations that produce the graph of \(g\) from the graph of \(y=\ln x\). b) Find the coordinates of the point on the graph where the tangent line is parallel to \(y=-x+4\).

Hints

- Read the effects of the factor and constant from the formula. - Parallel lines have equal slopes. - Set the derivative equal to the target slope. - Substitute the resulting input into the original function.

Solution

1. Multiply the y-values of \(\ln x\) by \(2\), reflect the graph across the x-axis, and then shift it up \(1\) unit. 2. The given line has slope \(-1\). Differentiate: \(g'(x)=-\frac{2}{x}\). Set the derivative equal to \(-1\): \(-\frac{2}{x}=-1\), so \(x=2\). The corresponding y-value is \(g(2)=1-2\ln2\).

Answer

a) Vertically stretch by a factor of \(2\), reflect across the x-axis, and shift up \(1\) unit. b) \((2, 1-2\ln2)\)
52951812
Let \(f(x)=e^{2x-4}\) and \(g(x)=e^x\). a) Find \(f'(x)\), and find the equation of the tangent line to the graph of \(f\) at \(x=2\). b) The graphs of \(f\) and \(g\) intersect at a point \(S\). Find the x-coordinate of \(S\). c) Show that at \(S\), the slope of the graph of \(f\) is twice the slope of the graph of \(g\).

Hints

- Use the chain rule for \(f\). - A tangent line needs a point and a derivative value. - Equal exponential expressions with the same base have equal exponents. - Compare the two derivative values at the intersection input.

Solution

1. By the chain rule, \(f'(x)=2e^{2x-4}\). At \(x=2\), \(f(2)=1\) and \(f'(2)=2\). Thus, the tangent line is \(y-1=2(x-2)\), or \(y=2x-3\). 2. At an intersection, \(e^{2x-4}=e^x\). Since the bases are equal and the exponential function is one-to-one, \(2x-4=x\), so \(x=4\). 3. Since \(g'(x)=e^x\), \(g'(4)=e^4\). Also, \(f'(4)=2e^{2\cdot4-4}=2e^4\). Therefore, \(f'(4)=2g'(4)\).

Answer

a) \(f'(x)=2e^{2x-4}\); tangent line: \(y=2x-3\) b) The x-coordinate of \(S\) is \(4\). c) \(f'(4)=2e^4=2g'(4)\).
52990312
A differentiable function can be approximated near a point by its tangent line. Let \(f(x)=\ln(x+1)\). a) Find the linearization \(L\) of \(f\) at \(P(0,f(0))\). b) Use \(L\) to approximate \(\ln(1.1)\), \(\ln(1.02)\), and \(\ln(0.95)\). c) Use the second derivative to determine the concavity of \(f\). Then decide whether each approximation in part b) is greater than or less than the exact value.

Hints

- Build \(L(x)\) from the function value and derivative at the center. - Match each logarithm to the form \(\ln(1+x)\). - Use the sign of the second derivative to decide where the graph lies relative to its tangent line.

Solution

1. Since \(f(0)=\ln(1)=0\) and \(f'(x)=\frac{1}{x+1}\), \(f'(0)=1\). 2. The linearization is \(L(x)=f(0)+f'(0)(x-0)=x\). Thus \(\ln(1+x)\approx x\) for \(x\) near \(0\). 3. For \(\ln(1.1)\), use \(x=0.1\): \(\ln(1.1)\approx L(0.1)=0.1\). 4. For \(\ln(1.02)\), use \(x=0.02\): \(\ln(1.02)\approx L(0.02)=0.02\). 5. For \(\ln(0.95)\), use \(x=-0.05\): \(\ln(0.95)\approx L(-0.05)=-0.05\). 6. The second derivative is \(f''(x)=-\frac{1}{(x+1)^2}<0\) for \(x>-1\). Therefore, \(f\) is concave down, and its tangent lines lie above the graph. Each approximation is greater than the corresponding exact value.

Answer

a) \(L(x)=x\) b) \(\ln(1.1)\approx0.1\); \(\ln(1.02)\approx0.02\); \(\ln(0.95)\approx-0.05\) c) The graph is concave down on \((-1,\infty)\), so all three linear approximations are overestimates.
52990412
Consider \(g(x)=\sqrt{x}\) near \(x_0=4\). a) Find the tangent-line approximation \(L(x)\) to \(g\) at \(x_0=4\). b) Use \(L(x)\) to approximate \(\sqrt{4.1}\), \(\sqrt{4.04}\), and \(\sqrt{3.9}\). c) Explain without a calculator why each approximation is an overestimate of the exact value.

Hints

- Use the point-slope form of the tangent line at \(x=4\). - Substitute each nearby x-value into your linear approximation. - Relate the sign of the second derivative to the position of a tangent line.

Solution

1. Since \(g(4)=2\) and \(g'(x)=\frac{1}{2\sqrt{x}}\), \(g'(4)=\frac{1}{4}\). 2. The tangent-line approximation is \(L(x)=2+\frac{1}{4}(x-4)=\frac{1}{4}x+1\). 3. \(L(4.1)=2+\frac{1}{4}(0.1)=2.025\). 4. \(L(4.04)=2+\frac{1}{4}(0.04)=2.01\). 5. \(L(3.9)=2+\frac{1}{4}(-0.1)=1.975\). 6. The second derivative is \(g''(x)=-\frac{1}{4x^{3/2}}<0\) for \(x>0\). Thus the graph is concave down, so its tangent line lies above the graph except at the point of tangency. Therefore, all three approximations are overestimates.

Answer

a) \(L(x)=\frac{1}{4}x+1\) b) \(\sqrt{4.1}\approx2.025\); \(\sqrt{4.04}\approx2.01\); \(\sqrt{3.9}\approx1.975\) c) Since \(g''(x)<0\) for \(x>0\), the graph is concave down and the tangent-line values are overestimates.
52994712
Let \(f(x)=\log_3x\), where \(x>0\). Find an equation of the tangent line to the graph at \(x_0=3\).

Hints

- Recall the derivative of \(\log_bx\). - Find the function value and derivative value at \(x=3\). - Use point-slope form. - Convert between base-3 and natural logarithms if needed.

Solution

1. The point on the graph is \(f(3)=\log_33=1\). 2. Differentiate: \(f'(x)=\frac{1}{x\ln3}\). Thus, the slope at \(x=3\) is \(f'(3)=\frac{1}{3\ln3}\). 3. Use point-slope form: \(y-1=\frac{1}{3\ln3}(x-3)\). Therefore, \(y=\frac{x}{3\ln3}+1-\frac{1}{\ln3}\).

Answer

\(y=\frac{x}{3\ln3}+1-\frac{1}{\ln3}\)
52995512
Let \(f(x)=\ln x\), where \(x>0\). 1. Find the tangent line at \(x_0=1\). 2. Use this tangent line as a linear approximation for \(\ln(1.08)\) and \(\ln(0.95)\). 3. Find the absolute error of the approximation for \(\ln(1.08)\), rounded to four decimal places.

Hints

- Find the function value and derivative value at \(x=1\). - Use the tangent line as the linearization. - Substitute the nearby inputs into the linearization. - Absolute error is the absolute difference between the estimate and actual value.

Solution

1. Since \(f'(x)=\frac{1}{x}\), \(f(1)=0\) and \(f'(1)=1\). Therefore, the tangent line is \(L(x)=x-1\). 2. Use \(\ln x\approx L(x)\) near \(x=1\): \(\ln(1.08)\approx0.08\) and \(\ln(0.95)\approx-0.05\). 3. Since \(\ln(1.08)\approx0.076961\), the absolute error is \(|0.08-\ln(1.08)|\approx0.0030\).

Answer

1. \(L(x)=x-1\) 2. \(\ln(1.08)\approx0.08\); \(\ln(0.95)\approx-0.05\) 3. Absolute error: \(0.0030\)
52995612
For small values of \(x\), the approximation \(\ln(1+x)\approx x\) is often used. 1. Justify this approximation using the derivative of \(g(x)=\ln(1+x)\) at \(x=0\). 2. Use the approximation to estimate \(\ln(1.003)\) and \(\ln(0.998)\). 3. Give an approximation for \(\ln\left(1+\frac{1}{n}\right)\) when \(n\) is a very large positive integer.

Hints

- Find the function value and slope at \(x=0\). - Write each logarithm in the form \(\ln(1+x)\). - The tangent line gives a nearby approximation. - Consider what happens to \(\frac{1}{n}\) as \(n\) grows.

Solution

1. The function satisfies \(g(0)=0\) and \(g'(x)=\frac{1}{1+x}\), so \(g'(0)=1\). Therefore, the tangent line at \(x=0\) is \(y=x\), which gives \(\ln(1+x)\approx x\) near \(0\). 2. For \(1.003=1+0.003\), \(\ln(1.003)\approx0.003\). For \(0.998=1-0.002\), \(\ln(0.998)\approx-0.002\). 3. When \(n\) is large, \(\frac{1}{n}\) is small, so \(\ln\left(1+\frac{1}{n}\right)\approx\frac{1}{n}\).

Answer

1. The tangent line to \(g(x)=\ln(1+x)\) at \(x=0\) is \(y=x\). 2. \(\ln(1.003)\approx0.003\); \(\ln(0.998)\approx-0.002\) 3. \(\ln\left(1+\frac{1}{n}\right)\approx\frac{1}{n}\)
52998912
Let \(f(x)=x^2\ln x\), where \(x>0\). Find an equation of the tangent line to the graph at \(x=1\).

Hints

- Find the point on the graph at \(x=1\). - Apply the product rule. - Evaluate the derivative at \(x=1\). - Use point-slope form.

Solution

1. Evaluate the function: \(f(1)=1^2\ln1=0\). 2. Differentiate using the product rule: \(f'(x)=2x\ln x+x\). At \(x=1\), \(f'(1)=1\). 3. The tangent line through \((1, 0)\) with slope \(1\) is \(y=x-1\).

Answer

\(y=x-1\)
53260712
The graph shows \(f(x)=0.5x+\cos x\), \(g(x)=\cos x\), and \(h(x)=0.5x\) on \([-2,8]\). a) Explain how the graph of \(f\) is obtained by adding the y-values of \(g\) and \(h\). Illustrate at \(x=0\). b) Find an equation of the tangent line to \(f\) at \(x_0=\pi\). c) Find all inputs in \([0,2\pi]\) where the graph of \(f\) has a horizontal tangent.
Figure for problem 532607

Hints

- Compare the three formulas term by term. - A tangent line requires both \(f(x_0)\) and \(f'(x_0)\). - A horizontal tangent has derivative value \(0\).

Solution

1. Since \(f(x)=g(x)+h(x)\), the y-coordinate on \(f\) is the sum of the corresponding y-coordinates on \(g\) and \(h\). At \(x=0\), \(f(0)=1\). 2. Differentiate: \(f'(x)=0.5-\sin x\). At \(x=\pi\), \(f'(\pi)=0.5\) and \(f(\pi)=\frac{\pi}{2}-1\). Thus, the tangent is \(t(x)=0.5x-1\). 3. Horizontal tangents satisfy \(\sin x=\frac{1}{2}\). On \([0,2\pi]\), the solutions are \(x=\frac{\pi}{6}\) and \(x=\frac{5\pi}{6}\).

Answer

a) Add corresponding y-values: \(f(x)=g(x)+h(x)\). At \(x=0\), \(f(0)=1\). b) \(t(x)=0.5x-1\) c) \(x=\frac{\pi}{6}\) and \(x=\frac{5\pi}{6}\)
55106112
The graph shows \(f(x)=\sqrt{x+1}\) together with its tangent line \(L\) at \(x=3\). a) Find \(L(x)\) and use it to approximate \(f(3.8)\). b) Using the graph, decide whether the approximation is an overestimate or an underestimate of \(f(3.8)\).
Figure for problem 551061

Hints

- Use the point and slope at the tangency input to build \(L\). - The target input is close to the point of tangency. - For the error direction, compare the vertical positions of the curve and tangent near the target input.

Solution

1. \(f(3)=2\), and \(f'(x)=\frac{1}{2\sqrt{x+1}}\), so \(f'(3)=\frac{1}{4}\). 2. Thus, \(L(x)=2+\frac{1}{4}(x-3)=\frac{1}{4}x+\frac{5}{4}\). 3. \(L(3.8)=2.2\), so \(f(3.8)\approx2.2\). 4. Near \(x=3.8\), the displayed tangent line lies above the curve. Therefore, \(2.2\) is an overestimate.

Answer

a) \(L(x)=\frac{1}{4}x+\frac{5}{4}\), so \(f(3.8)\approx2.2\). b) The approximation is an overestimate.
55106212
The graph shows \(f(x)=\ln x\) together with the tangent lines \(L_1\) at \(x=1\) and \(L_2\) at \(x=2\). a) Use each tangent line to approximate \(\ln(1.9)\). b) Which approximation should be better? Justify your choice using the centers of the linearizations and the graph.
Figure for problem 551062

Hints

- Build each tangent line from the function value and derivative at its own center. - Compare how far the target input lies from each center. - Use the graph to check which tangent follows the logarithm more closely near the target.

Solution

1. At \(x=1\), \(f(1)=0\) and \(f'(1)=1\), so \(L_1(x)=x-1\). Hence, \(L_1(1.9)=0.9\). 2. At \(x=2\), \(f(2)=\ln2\) and \(f'(2)=\frac{1}{2}\), so \(L_2(x)=\ln2+\frac{1}{2}(x-2)\). Hence, \(L_2(1.9)=\ln2-0.05\approx0.6431\). 3. The input \(1.9\) is much closer to the center \(2\) than to the center \(1\), and the graph shows \(L_2\) tracking \(f\) closely near \(1.9\). Therefore, \(L_2\) should give the better approximation.

Answer

a) From \(L_1\): \(0.9\). From \(L_2\): \(\ln2-0.05\approx0.6431\). b) \(L_2\) should be better because \(1.9\) is closer to its center \(x=2\), and the graph shows closer local agreement there.
55587012
Let \(f(x)=\sin x\), with angles measured in radians. a) Find the linearization \(L(x)\) at \(a=\frac{\pi}{6}\). b) Use it to approximate \(\sin\left(\frac{\pi}{6}+0.02\right)\). c) Without evaluating the exact sine value, determine whether the linear approximation is an overestimate or an underestimate. Justify using the sign of \(f''\) near the center.

Hints

- Use the exact sine and cosine values at the convenient center angle. - The nearby input differs from the center by only \(0.02\) radians. - The sign of the second derivative determines whether the graph bends above or below its tangent line locally.

Solution

1. \(f\left(\frac{\pi}{6}\right)=\frac{1}{2}\) and \(f'(x)=\cos x\), so \(f'\left(\frac{\pi}{6}\right)=\frac{\sqrt{3}}{2}\). 2. Thus \(L(x)=\frac{1}{2}+\frac{\sqrt{3}}{2}\left(x-\frac{\pi}{6}\right)\). 3. At \(x=\frac{\pi}{6}+0.02\), \(L(x)=\frac{1}{2}+0.01\sqrt{3}\approx0.51732\). 4. Since \(f''(x)=-\sin x<0\) near \(x=\frac{\pi}{6}\), the graph is concave down there, so the tangent line lies above the graph. The linear approximation is an overestimate.

Answer

a) \(L(x)=\frac{1}{2}+\frac{\sqrt{3}}{2}\left(x-\frac{\pi}{6}\right)\) b) \(\sin\left(\frac{\pi}{6}+0.02\right)\approx\frac{1}{2}+0.01\sqrt{3}\approx0.51732\) c) Overestimate, because \(f''(x)=-\sin x<0\) near \(\frac{\pi}{6}\).
52561012
Let \(f(x)=\sin x\) and \(g(x)=\cos x\) for \(x\in[0, \pi]\). a) Find the input \(x_P\) at which the tangent lines to the two graphs are parallel. b) Show that the product of the two tangent slopes at a common input \(x\) is \(h(x)=-\frac{1}{2}\sin(2x)\). c) Use part b to explain why there is no input in \([0, \pi]\) at which the two tangent lines are perpendicular. d) Find inputs \(x_1,x_2\in[0, \pi]\) such that the tangent to \(f\) at \(x_1\) is perpendicular to the tangent to \(g\) at \(x_2\).

Hints

- Parallel lines have equal slopes. - Use the double-angle identity for sine. - Perpendicular nonvertical lines have a slope product of \(-1\). - Use the maximum possible values of sine and cosine in part d.

Solution

1. The derivatives are \(f'(x)=\cos x\) and \(g'(x)=-\sin x\). Parallel tangents have equal slopes, so \(\cos x=-\sin x\). On \([0, \pi]\), this gives \(x_P=\frac{3\pi}{4}\). 2. The product of the slopes is \(f'(x)g'(x)=-\sin x\cos x=-\frac{1}{2}\sin(2x)\). 3. Perpendicular nonvertical lines require a slope product of \(-1\). That would require \(-\frac{1}{2}\sin(2x)=-1\), or \(\sin(2x)=2\), which is impossible. Therefore, no common input produces perpendicular tangents. 4. For different inputs, require \(\cos(x_1)[-\sin(x_2)]=-1\), so \(\cos(x_1)\sin(x_2)=1\). On \([0, \pi]\), this occurs when \(x_1=0\) and \(x_2=\frac{\pi}{2}\).

Answer

a) \(x_P=\frac{3\pi}{4}\) b) \(f'(x)g'(x)=-\frac{1}{2}\sin(2x)\) c) No such common input exists. d) \(x_1=0\), \(x_2=\frac{\pi}{2}\)
52563312
Let \(f(x)=2\sin x\) and \(g_c(x)=\cos(2x)+c\), where \(c\in\mathbb{R}\). Find all values of \(c\) for which the two graphs are tangent at one or more points.

Hints

- Tangent graphs have equal values and equal slopes at the same input. - Differentiate both functions. - Use the double-angle identity for sine. - Solve the derivative equation first, then use the value equation.

Solution

1. At a point of tangency, the function values and derivatives must be equal: \(f(x)=g_c(x)\) and \(f'(x)=g_c'(x)\). 2. The derivatives are \(f'(x)=2\cos x\) and \(g_c'(x)=-2\sin(2x)\). Set them equal and use \(\sin(2x)=2\sin x\cos x\): \(2\cos x=-4\sin x\cos x\), so \(2\cos x(1+2\sin x)=0\). 3. If \(\cos x=0\), then \(\sin x=1\) or \(-1\), and \(\cos(2x)=-1\). For \(\sin x=1\), the value equation gives \(2=-1+c\), so \(c=3\). For \(\sin x=-1\), it gives \(-2=-1+c\), so \(c=-1\). 4. If \(\sin x=-\frac{1}{2}\), then \(\cos(2x)=\frac{1}{2}\). The value equation gives \(-1=\frac{1}{2}+c\), so \(c=-\frac{3}{2}\).

Answer

\(c\in\left\{-\frac{3}{2},-1,3\right\}\)
52563412
The graphs of \(f(x)=\sin^2x\) and \(h_k(x)=k-\cos x\) are tangent at one or more points. Find all real values of \(k\) for which this is possible.

Hints

- Tangency requires equal function values and equal derivatives. - Use the chain rule to differentiate \(\sin^2x\). - Factor the derivative equation. - Use \(\sin^2x+\cos^2x=1\) in the remaining case.

Solution

1. At a point of tangency, \(f(x)=h_k(x)\) and \(f'(x)=h_k'(x)\). 2. Differentiate: \(f'(x)=2\sin x\cos x\) and \(h_k'(x)=\sin x\). Set the slopes equal: \(\sin x(2\cos x-1)=0\). 3. If \(\sin x=0\), then \(\cos x=1\) or \(-1\). When \(\cos x=1\), the value equation gives \(0=k-1\), so \(k=1\). When \(\cos x=-1\), it gives \(0=k+1\), so \(k=-1\). 4. If \(\cos x=\frac{1}{2}\), then \(\sin^2x=1-\frac{1}{4}=\frac{3}{4}\). The value equation gives \(\frac{3}{4}=k-\frac{1}{2}\), so \(k=\frac{5}{4}\).

Answer

\(k\in\left\{-1,1,\frac{5}{4}\right\}\)
52901612
Let \(f(x)=x^2-4x+5\). 1. Find an equation of the tangent line at \(P=(3,f(3))\). 2. Find the largest interval centered at \(x=3\) on which the tangent line's y-values differ from \(f(x)\) by at most \(0.04\).

Hints

- Find the tangent line using the derivative at \(x=3\). - Write the absolute difference between the function and tangent line. - Solving a squared inequality produces an absolute-value condition. - The endpoints occur where the error equals the allowed maximum.

Solution

1. Since \(f(3)=2\) and \(f'(x)=2x-4\), the tangent slope is \(f'(3)=2\). Therefore, the tangent line is \(y-2=2(x-3)\), or \(y=2x-4\). 2. The absolute error is \(|f(x)-(2x-4)|=|x^2-6x+9|=(x-3)^2\). 3. Require \((x-3)^2\le 0.04\). Then \(|x-3|\le 0.2\). 4. Therefore, \(2.8\le x\le 3.2\), so the largest interval is \([2.8,3.2]\).

Answer

1. \(y=2x-4\) 2. \([2.8,3.2]\)
55106312
A spherical part is designed with radius \(10.00\,\text{cm}\). Its volume is \(V(r)=\frac{4}{3}\pi r^3\). a) If the manufactured radius can differ from the design by as much as \(0.03\,\text{cm}\), use a linear approximation to estimate the maximum resulting volume error. b) A quality standard allows an estimated volume error of at most \(20\,\text{cm}^3\). According to the same linear approximation, what is the largest allowable radius error?

Hints

- Linearize the volume with respect to radius at the design radius. - For an error bound, use magnitudes of the small input and output changes. - In part b, work backward from the allowed output error to the permitted input error.

Solution

1. \(V'(r)=4\pi r^2\), so at \(r=10\), \(V'(10)=400\pi\). 2. For a small radius error \(\Delta r\), the volume error satisfies \(|\Delta V|\approx400\pi|\Delta r|\). 3. With \(|\Delta r|=0.03\), \(|\Delta V|\approx12\pi\,\text{cm}^3\approx37.70\,\text{cm}^3\). 4. For the quality standard, require \(400\pi|\Delta r|\le20\). Thus, \(|\Delta r|\le\frac{1}{20\pi}\,\text{cm}\approx0.0159\,\text{cm}\).

Answer

a) Approximately \(12\pi\,\text{cm}^3\approx37.70\,\text{cm}^3\). b) At most \(\frac{1}{20\pi}\,\text{cm}\approx0.0159\,\text{cm}\).

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