Answer:
1.68 ft
Step-by-step explanation:
Let x be the radius
Arc length = 3.14x
Width = 2x
Height = [12 - (2x) - 3.14x]/2
= 6 - 2.57x
Area = 3.14x²/2 + 2x(6 - 2.57x)
Area = 12x - 3.57x²
dA/dx = 12 - 7.14x = 0
x = 1.6806722689
Height = 6 - 2.57x
= 1.6806722689