Chapter 5: Problem 48
Evaluate the expression, if possible, or say what additional information is needed, given that \(\int_{-4}^{4} g(x) d x=12\). $$\int_{-4}^{4} g(-x) d x$$
Short Answer
Expert verified
The integral \(\int_{-4}^{4} g(-x) \, dx\) is 12.
Step by step solution
01
Recognize Even Function Property
A function is considered even if for all \(x\), \(g(x) = g(-x)\). This means that the function is symmetric with respect to the y-axis. Our goal is to check if the given function \(g(-x)\) has this property.
02
Analyze the Provided Integral
We are given \( \int_{-4}^{4} g(x) \, dx = 12 \). This means that the area under the curve \(g(x)\) from \(-4\) to \(4\) is 12.
03
Relationship between \(g(-x)\) and \(g(x)\)
Consider that for any function \(g(x)\), \(\int_{-a}^{a} g(-x) \, dx\) will have the same value as \(\int_{-a}^{a} g(x) \, dx\), provided that the function \(g(x)\) is even, because \(g(-x) = g(x)\).
04
Evaluate the Integral
Since we have \(\int_{-4}^{4} g(x) \, dx = 12\) and the integral from \(-a\) to \(a\) for an even function has the same value regardless of flipping the sign of \(x\), we find \(\int_{-4}^{4} g(-x) \, dx = 12\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Even Functions
Even functions are a special type of function where for every value of \( x \), the function yields the same result for \( -x \). This can be expressed mathematically as \( g(x) = g(-x) \). These functions exhibit symmetry about the y-axis.
Here are some properties of even functions:
Here are some properties of even functions:
- If you reflect the graph of an even function across the y-axis, it looks unchanged. This is visual symmetry.
- Typical examples include \( x^2, \, x^4, \, \text{and} \, \cos(x) \).
- The concept of even functions is crucial when evaluating certain kinds of integrals, as symmetry can simplify the calculations.
Definite Integrals
A definite integral is the calculation of the area under a curve between two limits, let's call them \( a \) and \( b \). It is represented as \( \int_{a}^{b} g(x) \, dx \). Definite integrals provide a numerical value that represents this area.
Key aspects of definite integrals:
Key aspects of definite integrals:
- The integral has upper and lower limits, \( a \) and \( b \), which define the start and end points on the x-axis.
- The result of a definite integral can be a positive or negative number, or even zero, indicating the net area between the curve and the x-axis.
- Adjustments can be made by calculating from \( -a \) to \( a \) in terms of symmetry, which particularly simplifies when dealing with even functions.
- In the context of our exercise, realizing \( \int_{-4}^{4} g(x) \, dx = 12 \) provides vital information when determining the symmetric counterpart integral \( \int_{-4}^{4} g(-x) \, dx \).
Symmetry in Integrals
Symmetry plays an important role in simplifying the computation of integrals. When a function is symmetric, it means that parts of its domain mirror each other in some way, leading to potential simplifications.
For even functions over symmetric limits, such as from \( -a \) to \( a \), this simplification is notably useful. Consider the integral \( \int_{-a}^{a} g(x) \, dx \):
For even functions over symmetric limits, such as from \( -a \) to \( a \), this simplification is notably useful. Consider the integral \( \int_{-a}^{a} g(x) \, dx \):
- If \( g(x) \) is even, then the area under \( g(x) \) from \( -a \) to \( a \) is simply twice the area from \( 0 \) to \( a \). This is because \( g(x) = g(-x) \).
- For the integral \( \int_{-4}^{4} g(x) \, dx \), symmetry informs us that examining \( \int_{-4}^{4} g(-x) \, dx \) under the same condition does not affect the outcome, hence it also equals 12.