Find the volume of the solid generated by rotating the infinite region in the first quadrant between y = ex and the x-axis about the x-axis. The volume is (Simplify your answer. Type an exact answer, using as needed.)

Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
Section: Chapter Questions
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**Problem Statement:**

Find the volume of the solid generated by rotating the infinite region in the first quadrant between \( y = e^{-x} \) and the x-axis about the x-axis.

---

**Solution Approach:**

To solve this problem, you will typically use the method of disks or washers for finding the volume of a solid of revolution.

**Step-by-step Explanation:**

1. **Identify the function and axis of rotation:**
   - Function: \( y = e^{-x} \)
   - Axis of rotation: x-axis

2. **Determine the intersection points:**
   - The region of interest is infinite along the x-axis as \( y = e^{-x} \) approaches zero.

3. **Set up the integral using the disk method:**
   - The radius of each disk is given by the function value at a particular x, which is \( e^{-x} \).
   - The volume \( V \) of the solid generated is given by the integral:

   \[
   V = \pi \int_{0}^{\infty} (e^{-x})^2 \, dx
   \]

4. **Simplify and solve the integral:**
   - Simplify the integrand: \( (e^{-x})^2 = e^{-2x} \)
   - The volume integral becomes:

   \[
   V = \pi \int_{0}^{\infty} e^{-2x} \, dx
   \]

5. **Evaluate the integral:**
   - The integral of \( e^{-2x} \) is \( -\frac{1}{2} e^{-2x} \).
   - Evaluate from 0 to \( \infty \):

   \[
   V = \pi \left[ -\frac{1}{2} e^{-2x} \right]_{0}^{\infty} = \pi \left( 0 + \frac{1}{2} \right) = \frac{\pi}{2}
   \]

**Final Answer:**

The volume is \( \frac{\pi}{2} \). 

(Simplify your answer. Type an exact answer, using \(\pi\) as needed.)
Transcribed Image Text:**Problem Statement:** Find the volume of the solid generated by rotating the infinite region in the first quadrant between \( y = e^{-x} \) and the x-axis about the x-axis. --- **Solution Approach:** To solve this problem, you will typically use the method of disks or washers for finding the volume of a solid of revolution. **Step-by-step Explanation:** 1. **Identify the function and axis of rotation:** - Function: \( y = e^{-x} \) - Axis of rotation: x-axis 2. **Determine the intersection points:** - The region of interest is infinite along the x-axis as \( y = e^{-x} \) approaches zero. 3. **Set up the integral using the disk method:** - The radius of each disk is given by the function value at a particular x, which is \( e^{-x} \). - The volume \( V \) of the solid generated is given by the integral: \[ V = \pi \int_{0}^{\infty} (e^{-x})^2 \, dx \] 4. **Simplify and solve the integral:** - Simplify the integrand: \( (e^{-x})^2 = e^{-2x} \) - The volume integral becomes: \[ V = \pi \int_{0}^{\infty} e^{-2x} \, dx \] 5. **Evaluate the integral:** - The integral of \( e^{-2x} \) is \( -\frac{1}{2} e^{-2x} \). - Evaluate from 0 to \( \infty \): \[ V = \pi \left[ -\frac{1}{2} e^{-2x} \right]_{0}^{\infty} = \pi \left( 0 + \frac{1}{2} \right) = \frac{\pi}{2} \] **Final Answer:** The volume is \( \frac{\pi}{2} \). (Simplify your answer. Type an exact answer, using \(\pi\) as needed.)
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