Circle O has a radius of 5. If the area of the yellow region is 20π, find x (in degrees).
The area of the whole circle is pi · 52 = 25pi.
The yellow area is 20pi, so the portion of the circle colored yellow is 20pi / 25pi or 4/5ths.
The number of degrees in the yellow portion of the circle is (4/5)·360o = 288o.
This leaves 360o - 288o = 72o for the angle in the triangle.
Now, you can calculate how many degrees are in the other angle of the triangle.