Math Problem Statement

A piece of wire of length 59 is​ cut, and the resulting two pieces are formed to make a circle and a square. Where should the wire be cut to ​(a) minimize and ​(b) maximize the combined area of the circle and the​ square? Question content area bottom Part 1 ​(a) Let x be the amount of wire used for the circle. What is the function​ A, the combined area of the circle and​ square, in terms of​ x? Aequals    StartFraction x squared Over 4 pi EndFraction plus StartFraction left parenthesis 59 minus x right parenthesis squared Over 16 EndFraction ​(Type an expression. Type an exact​ answer, using pi as​ needed.) Part 2 The interval of interest of the objective function is    left bracket 0 comma 59 right bracket. ​(Simplify your answer. Type your answer in interval​ notation.) Part 3 To minimize the combined​ area, the wire should be cut so that a length of    25.954 is used for the circle and a length of    33.046 is used for the square. ​(Round to the nearest thousandth as​ needed.) Part 4 ​(b) To maximize the combined​ area, the wire should be cut so that a length of    enter your response here is used for the circle and a length of    enter your response here is used for the square. ​(Round to the nearest thousandth as​ needed.)

Solution

To tackle the problem, we first need to derive the combined area function A(x)A(x) based on the wire lengths allocated to the circle and square.

Part 1: Combined Area Function

  1. Circle: Let xx be the length of wire used for the circle. The circumference CC of the circle is xx, so the radius rr is: r=x2πr = \frac{x}{2\pi} The area AcA_c of the circle is: Ac=πr2=π(x2π)2=x24πA_c = \pi r^2 = \pi \left(\frac{x}{2\pi}\right)^2 = \frac{x^2}{4\pi}

  2. Square: The remaining length of wire for the square is 59x59 - x. The perimeter PP of the square is 59x59 - x, so the side length ss is: s=59x4s = \frac{59 - x}{4} The area AsA_s of the square is: As=s2=(59x4)2=(59x)216A_s = s^2 = \left(\frac{59 - x}{4}\right)^2 = \frac{(59 - x)^2}{16}

  3. Combined Area: Therefore, the total area A(x)A(x) is: A(x)=Ac+As=x24π+(59x)216A(x) = A_c + A_s = \frac{x^2}{4\pi} + \frac{(59 - x)^2}{16}

Part 2: Interval of Interest

The interval for xx (the wire used for the circle) is from 0 to 59: [0,59][0, 59]

Part 3: Minimizing the Combined Area

To minimize the area, we can take the derivative of A(x)A(x), set it to zero, and solve for xx:

  1. Find the derivative: A(x)=12πx59x8A'(x) = \frac{1}{2\pi} x - \frac{59 - x}{8} Setting A(x)=0A'(x) = 0: x2π=59x8\frac{x}{2\pi} = \frac{59 - x}{8}

  2. Solve for xx: 8x=2π(59x)8x = 2\pi(59 - x) 8x+2πx=118π8x + 2\pi x = 118\pi x(8+2π)=118πx(8 + 2\pi) = 118\pi x=118π8+2π25.954x = \frac{118\pi}{8 + 2\pi} \approx 25.954

Thus, the lengths for minimizing the area are:

  • Circle: x25.954x \approx 25.954
  • Square: 59x33.04659 - x \approx 33.046

Part 4: Maximizing the Combined Area

To maximize the area, we note that the areas of both shapes increase with more wire allocated. Hence, to maximize the area, allocate all wire to one shape:

  1. All wire to the circle:

    • Circle: x=59x = 59
    • Square: 00
  2. All wire to the square:

    • Circle: 00
    • Square: 5959

However, typically, we want a balanced allocation for optimal areas. The critical points found through the first derivative will be evaluated to check for a maximum.

Summary:

  • For minimizing combined area: Circle = 25.95425.954, Square = 33.04633.046
  • For maximizing combined area: Circle = 5959, Square = 00 or Circle = 00, Square = 5959

If you have any questions or need further details, feel free to ask!

Further Exploration Questions:

  1. How does changing the total length of the wire affect the area?
  2. What are the implications of different shapes on the area calculations?
  3. Can we derive a general formula for any lengths of wire?
  4. How would this change if we introduced different shapes, like rectangles?
  5. What are practical applications of maximizing area with constrained lengths?

Tip: Consider using calculus to find optimal solutions in problems involving areas and perimeters.

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Math Problem Analysis

Mathematical Concepts

Calculus
Geometry
Optimization

Formulas

Area of circle: A_c = (x^2) / (4π)
Area of square: A_s = ((59 - x)^2) / 16
Combined area: A(x) = A_c + A_s

Theorems

Fundamental Theorem of Calculus
Optimization Theorem

Suitable Grade Level

Grades 11-12