Engineering Board Exam Reviewer · Optimization (Maxima and Minima) · medium

Find the maximum area of a rectangle that can be inscribed in a semicircle of radius 5, with one side on the diameter.

  1. 25
  2. 12.5
  3. 50
  4. 20

Answer

A. 25

Solution

Let the rectangle have half-width x and height y, with x2+y2=25. Area =2xy, so ( Area)2=4x2(25-x2). Maximizing gives x2=y2=12.5, so Area =2(12.5)=25.

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