Answer :
check the picture below.
so, if the semi-circle has a diameter of 36, then the radius is half that, or 18
[tex]\bf \textit{area of a semi-circle}\\\\ A=\cfrac{\pi r^2}{2}\quad \begin{cases} r=radius\\ -----\\ r=18 \end{cases}\implies A=\cfrac{\pi 18^2}{2}\implies A=\cfrac{324\pi }{2} \\\\\\ A=162\pi [/tex]
so, if the semi-circle has a diameter of 36, then the radius is half that, or 18
[tex]\bf \textit{area of a semi-circle}\\\\ A=\cfrac{\pi r^2}{2}\quad \begin{cases} r=radius\\ -----\\ r=18 \end{cases}\implies A=\cfrac{\pi 18^2}{2}\implies A=\cfrac{324\pi }{2} \\\\\\ A=162\pi [/tex]
