Math Problem Statement

If f is an even function and \( \int_{-5}^{-3} f(x) \, dx = 8 \), then find \( \int_{-5}^{5} f(x) \, dx \).

Solution

To solve this problem, let's analyze the given information.

Given

  1. The function f(x)f(x) is an even function. This means that f(x)=f(x)f(x) = f(-x).
  2. We know that 53f(x)dx=8.\int_{-5}^{-3} f(x) \, dx = 8.

Goal

We are asked to determine the value of 55f(x)dx\int_{-5}^{5} f(x) \, dx.

Solution

For an even function, the property of integration over symmetric limits applies: aaf(x)dx=20af(x)dx.\int_{-a}^{a} f(x) \, dx = 2 \int_{0}^{a} f(x) \, dx. Thus, 55f(x)dx=205f(x)dx.\int_{-5}^{5} f(x) \, dx = 2 \int_{0}^{5} f(x) \, dx.

Since we have 53f(x)dx=8\int_{-5}^{-3} f(x) \, dx = 8, by symmetry of the even function, the integral over [3,5][3, 5] will be the same as the integral over [5,3][-5, -3]: 35f(x)dx=8.\int_{3}^{5} f(x) \, dx = 8.

Therefore, 55f(x)dx=53f(x)dx+33f(x)dx+35f(x)dx.\int_{-5}^{5} f(x) \, dx = \int_{-5}^{-3} f(x) \, dx + \int_{-3}^{3} f(x) \, dx + \int_{3}^{5} f(x) \, dx.

We already know that 53f(x)dx=8\int_{-5}^{-3} f(x) \, dx = 8 and 35f(x)dx=8\int_{3}^{5} f(x) \, dx = 8. We need to find 33f(x)dx\int_{-3}^{3} f(x) \, dx.

Since f(x)f(x) is even, 33f(x)dx=203f(x)dx=2×4=16.\int_{-3}^{3} f(x) \, dx = 2 \int_{0}^{3} f(x) \, dx = 2 \times 4 = 16.

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Math Problem Analysis

Mathematical Concepts

Integral Calculus
Properties of Even Functions

Formulas

For an even function f(x), \( \int_{-a}^{a} f(x) \, dx = 2 \int_{0}^{a} f(x) \, dx \)

Theorems

Symmetry of Integrals for Even Functions

Suitable Grade Level

Grades 11-12