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Ch. 6 - Applications of Integration
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243당신이 사용하는 게 아니라요?교과서 변경
6장, 문제 6.3.34

Let R be the region bounded by the following curves. Find the volume of the solid generated when R is revolved about the given axis.


y=√sin x,y=1, and x=0; about the x-axis 

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First, identify the region R bounded by the curves: \( y = \sqrt{\sin x} \), \( y = 1 \), and \( x = 0 \). Determine the interval for \( x \) where these curves intersect and define the region. Since \( y = \sqrt{\sin x} \) is defined where \( \sin x \geq 0 \), consider \( x \) in \( [0, \pi] \) because \( \sin x \) is positive there, and find the point where \( \sqrt{\sin x} = 1 \) to find the upper bound of \( x \).
Next, sketch or visualize the region and the axis of rotation, which is the x-axis. Since the region is bounded above by \( y = 1 \) and below by \( y = \sqrt{\sin x} \), revolving around the x-axis will create a solid with a hole (washer) at each cross-section.
Set up the volume integral using the washer method. The volume \( V \) is given by integrating the area of the washers perpendicular to the x-axis over the interval found in step 1. The outer radius \( R_{outer} \) is the distance from the x-axis to \( y = 1 \), and the inner radius \( R_{inner} \) is the distance from the x-axis to \( y = \sqrt{\sin x} \). So, the volume integral is: \[ V = \pi \int_{0}^{a} \left( R_{outer}^2 - R_{inner}^2 \right) \, dx = \pi \int_{0}^{a} \left(1^2 - (\sqrt{\sin x})^2 \right) \, dx \] where \( a \) is the upper limit of integration found in step 1.
Simplify the integrand inside the integral. Since \( (\sqrt{\sin x})^2 = \sin x \), the integrand becomes \( 1 - \sin x \). So the volume integral simplifies to: \[ V = \pi \int_{0}^{a} (1 - \sin x) \, dx \]
Finally, evaluate the integral (without calculating the numerical value here). Use the antiderivative of \( 1 - \sin x \), which is \( x + \cos x \), and apply the limits from 0 to \( a \). This will give the expression for the volume of the solid generated by revolving the region about the x-axis.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Volume of Solids of Revolution

This concept involves finding the volume of a 3D solid formed by rotating a 2D region around an axis. Common methods include the disk/washer method and the shell method, which use integration to sum infinitesimal volumes. Understanding how to set up these integrals is essential for solving volume problems.
추천 영상:
04:48
Finding Volume Using Disks

Washer Method

The washer method calculates volume by slicing the solid perpendicular to the axis of rotation, creating washers (disks with holes). The volume is found by integrating the difference between the outer and inner radii squared, multiplied by π, over the interval. This method is useful when the region is bounded by two curves.
추천 영상:
07:33
Euler's Method

Setting up Integration Limits and Radii

Correctly identifying the limits of integration and the radii of washers or shells is crucial. The limits come from the intersection points of the bounding curves, and the radii depend on the distance from the axis of rotation to the curves. Accurate setup ensures the integral represents the volume correctly.
추천 영상:
가이드 코스
11:11
Improper Integrals: Infinite Intervals