In the figure below, , , and and are right angles. ∆GEM ∆RTO by:

1. Well for a circle, a central angle is formed by two radii.  A central angle is an angle with endpoints which is located on a circle's circumference and vertex which is located on a circle's center. So the measure of the central angle is equal to the measure of the intercepting arc.

2. An inscribed angle is an angle that is formed by two chords that meet at the same point on a circle. The measure of an inscribed angle is 1/2 the measure of its intercepted arc.

I think you could handle the rest of this problem hope it all helped!