Given the formula of a portion of the circle
[tex]A=\pi *r^2*\frac{\theta}{360}[/tex]
We are given that
[tex]A=20\pi ft^2[/tex][tex]\theta=72[/tex]
thus
[tex]20\pi=\pi *r^2*\frac{72}{360}[/tex]
Solving for r
[tex]20=r^2*\frac{1}{5}[/tex][tex]r^2=5*20[/tex][tex]r=\sqrt{100}[/tex][tex]r=10[/tex]
then the radius of the circle is 10ft
