Math Problem Statement

Kawat sepanjang 16 cm dipotong menjadi dua bagian. Salah satu potongan dibentuk menjadi bujur sangkar, dan potongan lainnya dibentuk menjadi lingkaran. Tentukan ukuran potongan agar: a) Jumlah seluruh luasnya minimum, b) Jumlah seluruh luasnya maksimum.

Solution

The problem in the image involves optimizing the use of a wire of 16 cm, which is divided into two parts. One part is used to form a square, and the other is used to form a circle. The goal is to determine the sizes of these parts to:

  1. Minimize the total area of the square and circle.
  2. Maximize the total area of the square and circle.

Let me break it down into a mathematical model.

Step 1: Define variables

  • Let xx be the length of the wire used for the square.
  • The remaining wire, 16x16 - x, is used for the circle.

Step 2: Relationships

  • Perimeter of the square: xx (so each side of the square is x4\frac{x}{4}).
  • Perimeter of the circle: 16x16 - x (so the radius of the circle is 16x2π\frac{16 - x}{2\pi}).

Areas:

  1. Area of the square: (x4)2=x216\left(\frac{x}{4}\right)^2 = \frac{x^2}{16}.
  2. Area of the circle: π(16x2π)2=(16x)24π\pi \left(\frac{16 - x}{2\pi}\right)^2 = \frac{(16 - x)^2}{4\pi}.

Step 3: Total area

The total area is: A(x)=x216+(16x)24π.A(x) = \frac{x^2}{16} + \frac{(16 - x)^2}{4\pi}.

Step 4: Optimization

a. Minimize total area

To find the value of xx that minimizes A(x)A(x), we take the derivative A(x)A'(x), set it to 0, and solve for xx.

b. Maximize total area

Similarly, we solve for xx that maximizes A(x)A(x).

Let me compute these solutions mathematically.import sympy as sp

Define variables

x = sp.symbols('x', positive=True) pi = sp.pi

Total area equation

A = (x**2 / 16) + ((16 - x)**2 / (4 * pi))

Derivative of the area

A_prime = sp.diff(A, x)

Solve for critical points

critical_points = sp.solve(A_prime, x)

Evaluate the second derivative to determine minima or maxima

A_double_prime = sp.diff(A_prime, x) results = [] for point in critical_points: curvature = A_double_prime.subs(x, point) area_value = A.subs(x, point) results.append((point, curvature, area_value))

Add endpoints x = 0 and x = 16 for comparison

endpoints = [(0, A.subs(x, 0)), (16, A.subs(x, 16))]

results, endpoints([(64/(pi + 4), 1/8 + 1/(2pi), (16 - 64/(pi + 4))**2/(4pi) + 256/(pi + 4)**2)], [(0, 64/pi), (16, 16)])([(64/(pi + 4), 1/8 + 1/(2pi), (16 - 64/(pi + 4))**2/(4pi) + 256/(pi + 4)**2)], [(0, 64/pi), (16, 16)])success

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Math Problem Analysis

Mathematical Concepts

Optimization
Geometry
Derivatives

Formulas

Area of a square: (side)^2
Perimeter of a square: 4 × side
Area of a circle: π × (radius)^2
Perimeter of a circle: 2π × radius

Theorems

Derivative Test for Optimization

Suitable Grade Level

Grades 10-12