Math Problem Statement

A Norman window has the shape of a rectangle surmounted by a semicircle. Find the dimensions of a Norman window of perimeter 40ft that will admit the greatest possible light. (Round the answers to two decimal places)

Solution

To maximize the amount of light admitted through a Norman window, we need to maximize the area of the window, given a fixed perimeter of 40 feet.

Problem Breakdown:

  1. Structure of the Norman Window:

    • The window consists of a rectangle topped by a semicircle.
    • Let the width of the rectangle (and diameter of the semicircle) be ww.
    • Let the height of the rectangle be hh.
  2. Perimeter Calculation:

    • The perimeter consists of the width ww, the two heights hh, and the semicircle perimeter.
    • The semicircle's perimeter is 12×2π×w2=πw2\frac{1}{2} \times 2\pi \times \frac{w}{2} = \frac{\pi w}{2}.
    • Total perimeter: P=w+2h+πw2P = w + 2h + \frac{\pi w}{2}.

    Given P=40P = 40 feet: 40=w+2h+πw240 = w + 2h + \frac{\pi w}{2}

    Simplifying for hh: h=40wπw22h = \frac{40 - w - \frac{\pi w}{2}}{2}

  3. Area Calculation:

    • The area AA of the window is the sum of the rectangle's area and the semicircle's area: A=wh+12π(w2)2=wh+πw28A = wh + \frac{1}{2}\pi\left(\frac{w}{2}\right)^2 = wh + \frac{\pi w^2}{8}

    Substituting hh from the perimeter equation: A(w)=w40wπw22+πw28A(w) = w \cdot \frac{40 - w - \frac{\pi w}{2}}{2} + \frac{\pi w^2}{8}

  4. Maximizing the Area:

    • We maximize A(w)A(w) with respect to ww by taking the derivative and setting it to zero.

Let's solve this to find the optimal dimensions ww and hh.The dimensions of the Norman window that will admit the greatest possible light, given a perimeter of 40 feet, are:

  • Width (w): 11.20 feet
  • Height (h): 5.60 feet

These values are rounded to two decimal places.

Would you like more details on how the optimization was done, or do you have any other questions?

Here are 8 related questions you might find interesting:

  1. How is the derivative used in optimization problems?
  2. What are critical points in calculus?
  3. Why does the semicircle influence the perimeter equation?
  4. Can the shape of the window affect the optimization result?
  5. What if the perimeter was different? How would the optimal dimensions change?
  6. How do we confirm that the solution is a maximum?
  7. What role does symmetry play in optimization problems?
  8. Can you provide a step-by-step solution to this problem?

Tip: Optimization problems often require balancing multiple constraints to find an ideal solution, such as maximizing area while minimizing material use.

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Math Problem Analysis

Mathematical Concepts

Geometry
Optimization

Formulas

Perimeter of a rectangle
Perimeter of a semicircle
Area of a rectangle
Area of a semicircle

Theorems

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Suitable Grade Level

Grades 10-12