Question

@Becki @ranga

Answer 1

I've drawn on the picture.

From the center of the circle, I've drawn out to D and E. This creates an isosceles triangle between C (center), D, and E. The angle C, by definition, is the angle of the arc it inscribes, in this case 108 degrees. Since the legs are the same length, you can figure out what the other 2 angles are.

Now, the segment from C to E is a right angle, by definition. So angle CED and angle DEF are complementary.