Math Problem Statement

Evaluate the integral of a piecewise function f(x) from 0 to 8, where f(x) is defined as 2x - 8 for 0 ≤ x < 4 and 8 - 2x for 4 ≤ x ≤ 8.

Solution

To solve the problem:

  1. Understand the function f(x)f(x):

    • For 0x<40 \leq x < 4, f(x)=2x8f(x) = 2x - 8, which is a linear function with a slope of 2 and y-intercept of -8.
    • For 4x84 \leq x \leq 8, f(x)=82xf(x) = 8 - 2x, which is also a linear function but decreasing (negative slope).
  2. Sketch the graph:

    • f(x)=2x8f(x) = 2x - 8: This line passes through (4,0)(4, 0) and (0,8)(0, -8).
    • f(x)=82xf(x) = 8 - 2x: This line passes through (4,0)(4, 0) and (8,0)(8, 0).
    • The graph forms two triangular regions: one below the x-axis (0x40 \leq x \leq 4) and one above the x-axis (4x84 \leq x \leq 8).
  3. Calculate areas of these regions:

    • Region 1 (0x40 \leq x \leq 4):
      • Base = 40=44 - 0 = 4
      • Height = 88
      • Area = 12×4×8=16\frac{1}{2} \times 4 \times 8 = 16 (below x-axis, so it contributes 16-16 to the integral).
    • Region 2 (4x84 \leq x \leq 8):
      • Base = 84=48 - 4 = 4
      • Height = 88
      • Area = 12×4×8=16\frac{1}{2} \times 4 \times 8 = 16 (above x-axis, so it contributes +16+16 to the integral).
  4. Evaluate the integral: 08f(x)dx=(16)+(16)=0\int_0^8 f(x) \, dx = (-16) + (16) = 0

Final Answer: 08f(x)dx=0\int_0^8 f(x) \, dx = 0

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Related Questions:

  1. How is the concept of signed area related to integrals?
  2. Can this approach be generalized for any piecewise function?
  3. Why is the integral zero if the positive and negative areas are equal?
  4. How does symmetry in the graph simplify integral calculations?
  5. What

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Math Problem Analysis

Mathematical Concepts

Piecewise Functions
Integrals
Area under a curve
Linear Functions
Signed Area

Formulas

Integral of a piecewise function
Area of a triangle = 1/2 * base * height

Theorems

Fundamental Theorem of Calculus
Area Interpretation of Definite Integrals

Suitable Grade Level

Grades 11-12