A piece of plexiglass is in the shape of a semicircle with radius 2 m. Determine the dimensions of the rectangle with the greatest area that can be cut from the piece of plexiglass.

The circle with radius 2m : x^2 + y^2 = 4

The semicircle: y=sqrt(4 - x^2)

The Area: A = 2xy = 2x(sqrt(4 - x^2))

Find A', simplify, and set 0:

x^2 - 2 = 0, and x = sqrt(2), y = sqrt(2)

Take A'' < 0 to verify maximum area.

Therefore, base length = 2x = 2 sqrt(2) meter

width = y = sqrt(2) meter

area = 4 square meter

Cut sqrt(2) away from the center both +, - x direction, and + y direction!