Trapezoid $ABCD$ is inscribed in the semicircle with diameter $\overline{AB}$, as shown below. If $CD = 7$, $AD = 3$, and $BC = 3$, then find the radius of the semicircle.

Use this to find your answer

I set up two equations, each with r and theta then I solved them simultaneously.

I only needed r so you can eliminate theta.