/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 28 Find the area of the indicated r... [FREE SOLUTION] | 91Ó°ÊÓ

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Find the area of the indicated region. We suggest you graph the curves to check whether one is above the other or whether they cross, and that you use technology to check your answers. Enclosed by \(y=x\) and \(y=x^{3}\)

Short Answer

Expert verified
The area enclosed by the functions \(y = x\) and \(y = x^3\) is \(\frac{1}{2}\).

Step by step solution

01

Find the Points of Intersection

To find the points of intersection, we need to set these two functions equal to each other: \(x = x^3\) To solve this equation, set the left side to 0 by subtracting the right side: \(0 = x^3 - x\) Next, factor out a common term, which is x: \(x(x^2 - 1) = 0\) Now we have a quadratic equation in the parentheses. We can further factor this equation: \(x(x - 1)(x + 1) = 0\) Now, we have found that the points of intersection occur when x = -1, x = 0, and x = 1. These correspond to the points (-1, -1), (0, 0), and (1, 1) respectively.
02

Calculate the Area by Integrating

To find the area between the curves, we will integrate the difference of the functions between the points of intersection found in step 1. Since the functions intersect between x = -1 and x = 1, we will use these values as limits of integration. The difference of the functions is given by: \[y = x - x^3\] Now we can set up the integral to find the area: \[A = \int_{-1}^{1} (x - x^3) dx\] To integrate this function, we will find the antiderivative: \[A = \frac{1}{2}x^2 - \frac{1}{4}x^4\] Now we will evaluate this antiderivative at the limits of integration: \[A = \frac{1}{2}(1)^2 - \frac{1}{4}(1)^4 - \left(\frac{1}{2}(-1)^2 - \frac{1}{4}(-1)^4\right)\] \[A = \frac{1}{2} - \frac{1}{4} - \frac{1}{2} + \frac{1}{4}\] \[A = 0\] However, since the area is enclosed, there is a possibility that one curve is above the other in one side of the interval and vice versa. To have an accurate result, we must split the range into two intervals and find the area for each interval prior to adding them up. We will consider the intervals from -1 to 0 and 0 to 1. For the interval from -1 to 0, the curve of \(y = x^3\) is above \(y = x\). Therefore, the area for this interval is given by: \[A_1 = \int_{-1}^{0} (x^3 - x) dx\] \[A_1 = \frac{1}{4}x^4 - \frac{1}{2}x^2\] \[A_1 = \frac{1}{4}(0)^4 - \frac{1}{2}(0)^2 - \left(\frac{1}{4}(-1)^4 - \frac{1}{2}(-1)^2\right)\] \[A_1 = \frac{1}{4}\] For the interval from 0 to 1, the curve of \(y = x\) is above \(y = x^3\). Therefore, the area for this interval is given by: \[A_2 = \int_{0}^{1} (x - x^3) dx\] \[A_2 = \frac{1}{2}x^2 - \frac{1}{4}x^4\] \[A_2 = \frac{1}{2}(1)^2 - \frac{1}{4}(1)^4 - \left(\frac{1}{2}(0)^2 - \frac{1}{4}(0)^4\right)\] \[A_2 = \frac{1}{4}\] Now we can add up the areas of both intervals: \[A = A_1 + A_2 = \frac{1}{4} + \frac{1}{4} = \frac{1}{2}\] So, the area enclosed by the functions \(y = x\) and \(y = x^3\) is \(\frac{1}{2}\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Point of Intersection
When we solve calculus problems involving the area between curves, the first thing we need to do is find where the curves intersect. These intersections help form the boundaries of the region we are interested in. In the given problem, we are looking at the functions \(y = x\) and \(y = x^3\). To find their points of intersection, set the equations equal to each other: \(x = x^3\).

This simplifies to \(x^3 - x = 0\). To solve, factor out an \(x\), yielding \(x(x^2 - 1) = 0\). Further factoring gives \(x(x - 1)(x + 1) = 0\). The solutions \(x = -1\), \(x = 0\), and \(x = 1\), represent the x-coordinates of the points where these functions intersect.

Using these x-values, we can find the corresponding points:
  • \((-1, -1)\)
  • \((0, 0)\)
  • \((1, 1)\)
These are crucial in defining the limits for integration and, consequently, the area between the curves.
Integration
Integration is the process of finding the area under a curve or between curves over a given interval. Once we have established the points of intersection, we can determine the area enclosed between the curves. By integrating the difference of the two functions, \(y = x^3\) and \(y = x\), over the interval defined by the intersection points, we compute the desired area.

In our problem, there are two sections to consider due to how the curves intersect. Between \(-1\) and \(0\), \(y = x^3\) is above \(y = x\). Between \(0\) and \(1\), \(y = x\) is above \(y = x^3\).

Thus, we calculate the area for each interval separately:
  • \(A_1 = \int_{-1}^{0} (x^3 - x)\, dx\)
  • \(A_2 = \int_{0}^{1} (x - x^3)\, dx\)
By adding these areas \(A_1\) and \(A_2\), we find the total area enclosed by \(y = x\) and \(y = x^3\).
Antiderivative
The antiderivative, or indefinite integral, represents a family of functions whose derivative is the original function you want to integrate. Finding it is a key step in evaluating definite integrals, which are used to calculate the area between curves.

When considering \(\int (x - x^3)\, dx\), we estimate the antiderivative of each part separately:
  • The antiderivative of \(x\) is \(\frac{1}{2}x^2\).
  • The antiderivative of \(-x^3\) is \(-\frac{1}{4}x^4\).
Combining these, we get the antiderivative: \[ \frac{1}{2}x^2 - \frac{1}{4}x^4 \].

Calculating the definite integral involves evaluating this antiderivative at the boundaries defined by the points of intersection, then finding the difference. This final step provides us the numerical area enclosed by the functions.
Limits of Integration
Limits of integration define the endpoints of the interval over which we integrate. They play a crucial role when calculating the area between two curves, as they mark the start and end points where the functions intersect each other.

In this problem, the curves \(y = x\) and \(y = x^3\) intersect at \(x = -1\), \(x = 0\), and \(x = 1\). These points serve as the limits of integration.

Because one curve changes position relative to the other at \(x = 0\), we split the interval from \(-1\) to \(1\) into two parts for accurate computation:
  • From \(-1\) to \(0\), where \(y = x^3\) is above \(y = x\).
  • From \(0\) to \(1\), where \(y = x\) is above \(y = x^3\).
By properly using these limits of integration and adjusting the functions accordingly, we ensure that the calculated area is correct.

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