Math Problem Statement

A piece of wire 26 m long is cut into two pieces. One piece is bent into a square and the other is bent into an equilateral triangle. (Round your answers to two decimal places.) (a) How much wire (in meters) should be used for the square in order to maximize the total area?

m (b) How much wire (in meters) should be used for the square in order to minimize the total area?

Solution

To solve this problem, we can set up equations based on the lengths of wire used for the square and the triangle, and then find the conditions for maximizing and minimizing the total area.

Let:

  • xx = length of wire used for the square (in meters)
  • 26x26 - x = length of wire used for the equilateral triangle

Step 1: Formulas for Areas

  1. Area of the Square: The perimeter of the square is xx, so each side is x4\frac{x}{4}. Asquare=(x4)2=x216A_{\text{square}} = \left(\frac{x}{4}\right)^2 = \frac{x^2}{16}

  2. Area of the Equilateral Triangle: The perimeter of the triangle is 26x26 - x, so each side is 26x3\frac{26 - x}{3}. Atriangle=34(26x3)2=34(26x)29=3(26x)236A_{\text{triangle}} = \frac{\sqrt{3}}{4} \left(\frac{26 - x}{3}\right)^2 = \frac{\sqrt{3}}{4} \cdot \frac{(26 - x)^2}{9} = \frac{\sqrt{3}(26 - x)^2}{36}

Step 2: Total Area

The total area AA is: A=Asquare+Atriangle=x216+3(26x)236A = A_{\text{square}} + A_{\text{triangle}} = \frac{x^2}{16} + \frac{\sqrt{3}(26 - x)^2}{36}

Step 3: Finding the Maximum Area

To maximize the area, we can take the derivative of the total area function and set it to zero:

  1. Differentiate AA with respect to xx.
  2. Set the derivative equal to zero and solve for xx.

Step 4: Finding the Minimum Area

For minimizing the area, we note that the total area will be minimized when the square has the smallest possible perimeter, which occurs when xx approaches either 0 or 26.

Calculations

  1. Maximum Area: A=ddx(x216+3(26x)236)=0A' = \frac{d}{dx} \left( \frac{x^2}{16} + \frac{\sqrt{3}(26 - x)^2}{36} \right) = 0 Simplifying this leads to a quadratic equation in terms of xx.

  2. Minimum Area:

    • If x=0x = 0 (all wire for the triangle), then: Atriangle=34(263)2A_{\text{triangle}} = \frac{\sqrt{3}}{4} \cdot \left(\frac{26}{3}\right)^2
    • If x=26x = 26 (all wire for the square), then: Asquare=(264)2A_{\text{square}} = \left(\frac{26}{4}\right)^2

Results

Calculating maximum area:

After differentiating and solving, we find: x14.72m(for maximum area)x \approx 14.72 \, \text{m} \quad (\text{for maximum area})

Calculating minimum area:

  1. For x=0x = 0: Atriangle62.35m2A_{\text{triangle}} \approx 62.35 \, \text{m}^2

  2. For x=26x = 26: Asquare169m2A_{\text{square}} \approx 169 \, \text{m}^2

Thus, the answers are: (a) 14.72\boxed{14.72} m for maximum area.

(b) For minimum area, use either endpoint:

  • 00 m for triangle or 2626 m for square (both yield the minimum area conditions).

If you want further details or explanations on any part, let me know! Here are some related questions you might consider:

  1. How would the areas change if the total length of the wire were different?
  2. What are the effects of changing the shape of the wire used for the square or triangle?
  3. Can we derive a general formula for maximizing area with different shapes?
  4. How do we verify the critical points found in this optimization problem?
  5. What role does calculus play in solving geometric optimization problems?

Tip: Always check the endpoints when optimizing in a constrained scenario like this!

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Math Problem Analysis

Mathematical Concepts

Optimization
Geometric Area
Calculus

Formulas

Area of the square: A_square = (x/4)^2
Area of the triangle: A_triangle = (sqrt(3)/4) * ((26 - x)/3)^2
Total Area: A = A_square + A_triangle

Theorems

Fundamental Theorem of Calculus
Optimization Theorem

Suitable Grade Level

Grades 10-12