Chapter 4: Problem 26
Evaluate \(\int_{-100}^{100}\left(x^{3}+\sin ^{5} x\right) d x\)
Short Answer
Expert verified
The integral evaluates to 0.
Step by step solution
01
Break Down the Integral
First, separate the integral into two different integrals: \( \int_{-100}^{100} x^3\, dx \) and \( \int_{-100}^{100} \sin^5 x \; dx \). This is possible because the integral of a sum is the sum of the integrals.
02
Evaluate the Symmetry of Each Function
The integrand \( \sin^5 x \) is an odd function because it is a sine function raised to an odd power, and \( x^3 \) is also an odd function. Integrals of odd functions over symmetric intervals around the origin, such as \([-a, a]\), evaluate to zero.
03
Apply Symmetry Property
For the integral \( \int_{-100}^{100} x^3\, dx \) and \( \int_{-100}^{100} \sin^5 x \; dx \), since both \(x^3\) and \(\sin^5 x\) are odd functions over the interval \([-100, 100]\), both integrals equal zero.
04
Combine the Results
Since both integrals evaluated to zero, the original integral \( \int_{-100}^{100} \left(x^3 + \sin^5 x\right) dx \) is the sum of the two, which is \(0 + 0 = 0\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Odd Functions
In mathematics, an odd function is a function that satisfies the condition \( f(-x) = -f(x) \) for all \( x \) in the function's domain. This means that if you flip the function around the y-axis and then around the x-axis, it looks the same. Graphically, odd functions have rotational symmetry around the origin, or they look the same if rotated 180 degrees.
Some common examples of odd functions include:
Some common examples of odd functions include:
- \( x^3 \)
- \( \sin(x) \)
- \( x^5 \)
Symmetry Property
The symmetry property of integrals is a valuable tool in integral calculus, especially when dealing with odd functions. This property refers to the effects of function symmetry on the outcome of definite integrals. If a function is odd,
This is because the areas above and below the x-axis cancel each other out. In our example, both \( x^3 \) and \( \sin^5(x) \) are integrated over the interval \([-100, 100]\), which is symmetrical.
Here are some points to note about symmetry:
- and it is integrated over an interval that is symmetric about the origin, \([-a, a]\),
This is because the areas above and below the x-axis cancel each other out. In our example, both \( x^3 \) and \( \sin^5(x) \) are integrated over the interval \([-100, 100]\), which is symmetrical.
Here are some points to note about symmetry:
- Even functions are symmetrical about the y-axis, and \( f(x) = f(-x) \).
- For even functions, the integral over a symmetric interval does not necessarily result in zero.
Definite Integrals
A definite integral is a type of integral that calculates the "net area" under a curve, between two specified points. The notation \( \int_a^b f(x) \, dx \) is used to represent a definite integral of the function \( f(x) \) from point \( a \) to point \( b \).
Definite integrals have numerous applications, such as calculating areas, volumes, and even probabilities in more advanced settings. When integrals have limits that are the same (as with \([-a, a]\) in our problem), this symmetry can be used to simplify calculations.
In working with definite integrals, particularly in the context of odd functions:
Definite integrals have numerous applications, such as calculating areas, volumes, and even probabilities in more advanced settings. When integrals have limits that are the same (as with \([-a, a]\) in our problem), this symmetry can be used to simplify calculations.
In working with definite integrals, particularly in the context of odd functions:
- The results can often be obtained quickly by recognizing symmetry properties, as noted above.
- The integral of an odd function over a symmetric interval \([-a, a]\) will always be zero.
- You can return to fundamental definitions or graphical interpretations if ever in doubt about the problem's setup.