The cross section of an air-conditioning duct is in the shape of a square with semicircles on each side?

Question

Express the area A of this cross section as a function of the diameter D (in cm) of the circular part

Answer 1

You have the square part: D^2
And you have a whole circle: (D/2)^2 * pi

D^2 + (D/2)^2*pi

D^2 * (1 + pi/4)

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