Chapter 4: Problem 79
Find the average value \(f_{\text {av }}\) of the function over the indicated interval. $$ f(x)=\frac{x}{\sqrt{2} ;} ;[0,3] $$
Short Answer
Expert verified
The average value of the function \(f(x) = \frac{x}{\sqrt{2}}\) over the interval \([0, 3]\) is \(f_{av} = \frac{3}{2\sqrt{2}}\).
Step by step solution
01
Write down Average Value formula
The average value of the function is given by the formula:
$$
f_{av} = \frac{1}{b - a}\int_{a}^{b} f(x)dx
$$
In our case, \(a=0\), \(b=3\) and \(f(x)=\frac{x}{\sqrt{2}}\).
02
Substitute values into the Average Value formula
Substitute the given values into the formula:
$$
f_{av} = \frac{1}{3 - 0}\int_{0}^{3} \frac{x}{\sqrt{2}} dx
$$
03
Calculate the integral
Calculate the integral of the function \(\frac{x}{\sqrt{2}}\) from 0 to 3:
$$
\int_{0}^{3} \frac{x}{\sqrt{2}} dx = \frac{1}{\sqrt{2}}\int_{0}^{3} x dx
$$
Now integrate x:
$$
\frac{1}{\sqrt{2}}\left[\frac{1}{2}x^2\right]_{0}^{3} = \frac{1}{\sqrt{2}}\left[\frac{1}{2}(3)^2 - \frac{1}{2}(0)^2\right]
$$
04
Simplify the expression
Simplify the expression to find the integral value:
$$
\frac{1}{\sqrt{2}}\left[\frac{1}{2}(9)\right] = \frac{9}{2\sqrt{2}}
$$
05
Divide integral by the width of the interval
Now divide the integral value by the width of the interval, which is 3:
$$
f_{av} = \frac{1}{3}\cdot\frac{9}{2\sqrt{2}} = \frac{9}{6\sqrt{2}}
$$
06
Simplify the expression and write the answer
Simplify the expression to obtain the average value of the function over the interval \([0, 3]\):
$$
f_{av} = \frac{3}{2\sqrt{2}}
$$
So, the average value of the function \(f(x) = \frac{x}{\sqrt{2}}\) over the interval \([0, 3]\) is \(\frac{3}{2\sqrt{2}}\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Average Value of Function
In Calculus, the average value of a function on a closed interval \[a, b\], helps us understand the "central tendency" of the function over that interval. It's like finding the arithmetic mean, but for a continuous function.
To calculate the average value of a function \(f(x)\) over an interval \[a, b\], we use this formula:
To calculate the average value of a function \(f(x)\) over an interval \[a, b\], we use this formula:
- \( f_{av} = \frac{1}{b - a}\int_{a}^{b} f(x)\,dx \)
- The average value \(f_{av}\) is the integral of the function over the interval, divided by the length of the interval \((b - a)\).
Definite Integral
The definite integral is a major concept in Calculus which helps in finding the net area under a curve defined by a function \(f(x)\) from one point to another, usually known as \[a, b\].
It is represented as:
It is represented as:
- \(\int_{a}^{b} f(x)\,dx\)
- The total area taking into account areas above and below the x-axis, signifying positive and negative values.
- Helps in determining total accumulation of quantities, and in the context of this problem, helps to find the overall 'effect' of a function over an interval.
Function Integration
Function integration is the process of finding the integral of a function, and it's crucial for calculating areas under curves and solving differential equations. This involves finding a new function whose derivative matches the original function, known as the anti-derivative.
In the problem at hand:
In the problem at hand:
- We integrate \(\frac{x}{\sqrt{2}}\) over the interval from 0 to 3.
- \(\int_{0}^{3} \frac{x}{\sqrt{2}} \,dx = \frac{1}{\sqrt{2}}\left[\frac{1}{2}x^2\right]_{0}^{3}\)
- This technique is part of a larger technique called the Fundamental Theorem of Calculus, which links the operation of differentiation to integration.
Mathematical Formula
Mathematical formulas serve as the cornerstone for problem-solving in Calculus and beyond. They provide a structured approach to solving complex problems and often reveal deep insights about relationships between variables.
In this exercise, the formula for the average value of a function is applied:
In this exercise, the formula for the average value of a function is applied:
- \( f_{av} = \frac{1}{b - a}\int_{a}^{b} f(x) \,dx \) simplifies the process of finding average values over an interval.
- Substituting known values to move towards a solution (like plugging in \(a=0\), \(b=3\), and the function \(f(x)=\frac{x}{\sqrt{2}}\)).
- Simplifying expressions and calculations to get the final answer.