Use the shell method to find the volume of the solid generated by revolving the region bounded by the graphs of the equations about the y-axis. y = 1 x21 y = 0, x = 4, x = 9

Calculus: Early Transcendentals
8th Edition
ISBN:9781285741550
Author:James Stewart
Publisher:James Stewart
Chapter1: Functions And Models
Section: Chapter Questions
Problem 1RCC: (a) What is a function? What are its domain and range? (b) What is the graph of a function? (c) How...
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### Problem 2

**Objective:**

Use the shell method to find the volume of the solid generated by revolving the region bounded by the graphs of the equations about the y-axis.

**Given:**

\[ y = \frac{1}{x^2} \]
\[ y = 0 \]
\[ x = 4 \]
\[ x = 9 \]

**Approach:**

To find the volume of the solid using the shell method, we need to set up and evaluate the integral. The shell method formula for a solid of revolution around the y-axis is:

\[
V = 2\pi \int_{a}^{b} \left(\text{radius}\right) \left(\text{height}\right) \, dx
\]

In this problem:
- The "radius" is the distance from the y-axis, which is \(x\).
- The "height" is the value of the function \(y = \frac{1}{x^2}\).

Substitute the limits of integration \(a = 4\) and \(b = 9\) into the formula.

Therefore, the volume \(V\) is given by:

\[
V = 2\pi \int_{4}^{9} x \left( \frac{1}{x^2} \right) \, dx
\]

Simplify the integral:

\[
V = 2\pi \int_{4}^{9} \frac{1}{x} \, dx
\]

Evaluate the integral:

\[
V = 2\pi \left[ \ln|x| \right]_{4}^{9}
\]

Calculating the definite integral:

\[
V = 2\pi \left( \ln 9 - \ln 4 \right)
\]

Simplify using properties of logarithms:

\[
V = 2\pi \ln\left(\frac{9}{4}\right)
\]

Thus, the volume of the solid is:

\[
V = 2\pi \ln\left(\frac{9}{4}\right)
\]

**Conclusion:**

The volume of the solid generated by revolving the given region about the y-axis is \( 2\pi \ln\left(\frac{9}{4}\right) \) cubic units.
Transcribed Image Text:### Problem 2 **Objective:** Use the shell method to find the volume of the solid generated by revolving the region bounded by the graphs of the equations about the y-axis. **Given:** \[ y = \frac{1}{x^2} \] \[ y = 0 \] \[ x = 4 \] \[ x = 9 \] **Approach:** To find the volume of the solid using the shell method, we need to set up and evaluate the integral. The shell method formula for a solid of revolution around the y-axis is: \[ V = 2\pi \int_{a}^{b} \left(\text{radius}\right) \left(\text{height}\right) \, dx \] In this problem: - The "radius" is the distance from the y-axis, which is \(x\). - The "height" is the value of the function \(y = \frac{1}{x^2}\). Substitute the limits of integration \(a = 4\) and \(b = 9\) into the formula. Therefore, the volume \(V\) is given by: \[ V = 2\pi \int_{4}^{9} x \left( \frac{1}{x^2} \right) \, dx \] Simplify the integral: \[ V = 2\pi \int_{4}^{9} \frac{1}{x} \, dx \] Evaluate the integral: \[ V = 2\pi \left[ \ln|x| \right]_{4}^{9} \] Calculating the definite integral: \[ V = 2\pi \left( \ln 9 - \ln 4 \right) \] Simplify using properties of logarithms: \[ V = 2\pi \ln\left(\frac{9}{4}\right) \] Thus, the volume of the solid is: \[ V = 2\pi \ln\left(\frac{9}{4}\right) \] **Conclusion:** The volume of the solid generated by revolving the given region about the y-axis is \( 2\pi \ln\left(\frac{9}{4}\right) \) cubic units.
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