Chapter 5: Problem 10
Find the average value of the function over the given interval. $$ f(x)=\frac{1}{\sqrt{1-x^{2}}} ;\left[-\frac{1}{2}, 0\right] $$
Short Answer
Expert verified
The average value is \( \frac{\pi}{3} \).
Step by step solution
01
Identify the Formula for Average Value of a Function
The average value of a function \( f(x) \) over the interval \([a, b]\) is given by the formula: \( \text{average value} = \frac{1}{b-a} \int_{a}^{b} f(x) \, dx \).
02
Set up the Integral
Using the given function \( f(x) = \frac{1}{\sqrt{1-x^{2}}} \) and interval \([-\frac{1}{2}, 0]\), set up the integral for the average value formula: \( \frac{1}{0 + \frac{1}{2}} \int_{-\frac{1}{2}}^{0} \frac{1}{\sqrt{1-x^2}} \, dx \).
03
Simplify the Factor Outside the Integral
The factor outside the integral is \( \frac{1}{0.5} = 2 \), so the expression becomes: \( 2 \int_{-\frac{1}{2}}^{0} \frac{1}{\sqrt{1-x^2}} \, dx \).
04
Evaluate the Integral
The integral \( \int \frac{1}{\sqrt{1-x^2}} \, dx \) is recognized as the inverse sine function \( \sin^{-1}(x) \). Therefore, \( \int_{-\frac{1}{2}}^{0} \frac{1}{\sqrt{1-x^2}} \, dx = \sin^{-1}(0) - \sin^{-1}\left(-\frac{1}{2}\right) \).
05
Calculate the Inverse Sine Values
Calculate the inverse sine: \( \sin^{-1}(0) = 0 \) and \( \sin^{-1}\left(-\frac{1}{2}\right) = -\frac{\pi}{6} \).
06
Substitute the Values Back and Simplify
Substitute back into the expression: \( 2 \left(0 - \left(-\frac{\pi}{6}\right)\right) = 2 \times \frac{\pi}{6} = \frac{\pi}{3} \). Thus, the average value is \( \frac{\pi}{3} \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Integral Calculus
Understanding integral calculus is essential for finding the average value of a function over a specific interval. Integral calculus involves finding the area under the curve of a function, which is represented by the definite integral. To calculate the average value of a function, we use the formula:
- \( \text{average value} = \frac{1}{b-a} \int_{a}^{b} f(x) \, dx \)
Inverse Trigonometric Functions
Inverse trigonometric functions, such as the inverse sine function used in this exercise, play a crucial role in solving integrals involving trigonometric expressions. The function \( \frac{1}{\sqrt{1-x^2}} \) can be recognized as the derivative of the inverse sine function, \( \sin^{-1}(x) \). This recognition allows us to evaluate the integral more easily. The general formula for finding the inverse sine integral is:
- \( \int \frac{1}{\sqrt{1-x^2}} \, dx = \sin^{-1}(x) + C \)
- \( \sin^{-1}(0) = 0 \)
- \( \sin^{-1}\left(-\frac{1}{2}\right) = -\frac{\pi}{6} \)
Definite Integral Evaluation
Definite integral evaluation refers to computing the integral of a function over a specified interval, which gives us a specific numerical result rather than a general expression involving a constant of integration. This process is essential for real-world applications, including finding areas, accumulated values, and average values.To evaluate the definite integral in this exercise, \( \int_{-\frac{1}{2}}^{0} \frac{1}{\sqrt{1-x^2}} \, dx \), you need to:
- Identify the antiderivative, here \( \sin^{-1}(x) \).
- Substitute the limits of integration into the antiderivative: \( \sin^{-1}(0) - \sin^{-1}\left(-\frac{1}{2}\right) \).
- Calculate the result of the subtraction, ensuring each trigonometric value is correctly evaluated.