Math Problem Statement

From the coordinates ((0,0)), a man walks (2) miles north to ((0,2)). He then walks along the path described by the curve (f(x) = \sin\left(\dfrac{\pi x}{2} \right) + 2 ) until he reaches the point ((2,2)). He then walks south for (2) miles, and finally walks west for (2) miles to return to his starting point. What is the total area contained by the path he walked?

Solution

To calculate the total area enclosed by the man's path, we divide the area into three distinct regions and calculate each separately:

  1. Region A: The area under the curve f(x)=sin(πx2)+2f(x) = \sin\left(\frac{\pi x}{2}\right) + 2 from x=0x = 0 to x=2x = 2.
  2. Region B: The area of the vertical segment connecting (2,2)(2,2) to (2,0)(2,0).
  3. Region C: The area of the rectangle from (2,0)(2,0) to (0,0)(0,0).

Step 1: Area under f(x)f(x)

The function is f(x)=sin(πx2)+2f(x) = \sin\left(\frac{\pi x}{2}\right) + 2. We integrate f(x)f(x) from x=0x = 0 to x=2x = 2:

Area under the curve=02(sin(πx2)+2)dx.\text{Area under the curve} = \int_0^2 \left(\sin\left(\frac{\pi x}{2}\right) + 2\right) \, dx.

Break the integral into two parts:

02sin(πx2)dx+022dx.\int_0^2 \sin\left(\frac{\pi x}{2}\right) dx + \int_0^2 2 \, dx.

  1. First term: Solve 02sin(πx2)dx\int_0^2 \sin\left(\frac{\pi x}{2}\right) dx: Let u=πx2u = \frac{\pi x}{2}, so du=π2dxdu = \frac{\pi}{2} dx, or dx=2πdudx = \frac{2}{\pi} du. Change the limits:

    • When x=0x = 0, u=0u = 0.
    • When x=2x = 2, u=πu = \pi.

    The integral becomes: 02sin(πx2)dx=2π0πsin(u)du.\int_0^2 \sin\left(\frac{\pi x}{2}\right) dx = \frac{2}{\pi} \int_0^\pi \sin(u) \, du.

    The integral of sin(u)\sin(u) is cos(u)-\cos(u): [ \frac{2}{\pi} \int_0^\pi \sin(u) , du = \frac{2}{\pi} \left[ -\cos(u) \right]_0^\pi = \frac{2}{\pi} \left[ -\cos(\pi) + \cos(0) \right]. ]

    Using cos(π)=1\cos(\pi) = -1 and cos(0)=1\cos(0) = 1: 2π[(1)+1]=2π(1+1)=4π.\frac{2}{\pi} \left[ -(-1) + 1 \right] = \frac{2}{\pi} (1 + 1) = \frac{4}{\pi}.

  2. Second term: Solve 022dx\int_0^2 2 \, dx: 022dx=2x02=2(2)2(0)=4.\int_0^2 2 \, dx = 2x \big|_0^2 = 2(2) - 2(0) = 4.

Adding the two parts: Area under the curve=4π+4.\text{Area under the curve} = \frac{4}{\pi} + 4.

Step 2: Area of the rectangle (Region C)

The rectangle has a width of 22 and a height of 22. Its area is: Area of the rectangle=2×2=4.\text{Area of the rectangle} = 2 \times 2 = 4.

Step 3: Total enclosed area

The total enclosed area is the sum of the areas from Steps 1 and 2: Total area=(4π+4)+4=4π+8.\text{Total area} = \left(\frac{4}{\pi} + 4\right) + 4 = \frac{4}{\pi} + 8.

Final Answer:

The total area contained by the path is: 4π+8square miles.\boxed{\frac{4}{\pi} + 8 \, \text{square miles}.}


Would you like further clarification on any step? Here are related questions to explore:

  1. How is the integral of trigonometric functions calculated?
  2. Why does the rectangle contribute to the total area?
  3. How do limits of integration affect area calculations?
  4. Can this problem be solved geometrically without integration?
  5. What if the curve was a different trigonometric function?

Tip: Always double-check your limits and substitutions when working with definite integrals!

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Math Problem Analysis

Mathematical Concepts

Definite Integration
Area Under a Curve
Geometry
Trigonometric Functions

Formulas

Area under a curve = ∫[a to b] f(x) dx
Area of a rectangle = width × height

Theorems

Fundamental Theorem of Calculus
Properties of Sine Function

Suitable Grade Level

Grades 10-12