Math Problem Statement

Compute the integral \( \int_{-3}^{13} f(x) \, dx \) where the graph of \( f(x) \) is the red curve given in the figure.

Solution

The problem asks to compute the integral 313f(x)dx\int_{-3}^{13} f(x) \, dx where the graph of f(x)f(x) is represented by the red curve, and all relevant points have integer coordinates.

From the graph, we can identify that the function f(x)f(x) is a piecewise function composed of:

  1. A linear segment from x=3x = -3 to x=4x = 4.
  2. A semi-circular arc from x=4x = 4 to x=12x = 12.
  3. A constant value from x=12x = 12 to x=13x = 13.

Step-by-step breakdown:

  1. Linear segment from x=3x = -3 to x=4x = 4: The line passes through points (3,3)(-3, -3) and (4,4)(4, 4). The equation of this line can be determined using the slope-intercept form: f(x)=xf(x) = x Hence, the integral over this interval is: 34xdx=[x22]34=422(3)22=84.5=3.5\int_{-3}^{4} x \, dx = \left[ \frac{x^2}{2} \right]_{-3}^{4} = \frac{4^2}{2} - \frac{(-3)^2}{2} = 8 - 4.5 = 3.5

  2. Semi-circular arc from x=4x = 4 to x=12x = 12: This section represents a semi-circle with radius 4 (centered at (8,4)(8, 4)) and height 4. The area of a semi-circle is: Area=12πr2=12π(4)2=8π\text{Area} = \frac{1}{2} \pi r^2 = \frac{1}{2} \pi (4)^2 = 8\pi Since we are calculating an integral, we directly add the area under the curve: 412f(x)dx=8π\int_{4}^{12} f(x) \, dx = 8\pi

  3. Constant segment from x=12x = 12 to x=13x = 13: The function has a constant value of f(x)=0f(x) = 0, so: 12130dx=0\int_{12}^{13} 0 \, dx = 0

Total Integral:

Combining all contributions, the total integral is: 313f(x)dx=3.5+8π+0=3.5+8π\int_{-3}^{13} f(x) \, dx = 3.5 + 8\pi + 0 = 3.5 + 8\pi

So, the exact answer is: 3.5+8π\boxed{3.5 + 8\pi}

Let me know if you would like more details or have further questions!

Here are 5 questions related to this problem:

  1. How do you derive the equation of a line between two points?
  2. What is the formula for the area of a circle and how is it applied in integrals?
  3. How would the integral change if the semi-circle were a full circle?
  4. What are the rules for integrating piecewise functions?
  5. Can you find the integral using numerical methods if the shape was more complex?

Tip: For semi-circles and other geometric shapes, converting the area into an integral helps break complex problems into simpler parts.

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Math Problem Analysis

Mathematical Concepts

Integral Calculus
Piecewise Functions
Area Under Curves

Formulas

Area of a semi-circle: \( \frac{1}{2} \pi r^2 \)
Integral of a linear function: \( \int_{a}^{b} mx + c \, dx \)

Theorems

Fundamental Theorem of Calculus
Properties of Definite Integrals

Suitable Grade Level

Grades 11-12 and College Calculus