Problem: To prove that opposite angles of an inscribed quadrilateral are supplementary.
First construct a circle.
Then add four points on the circle and create an inscribed quadrilateral.
Construct a segment AC. This will create two triangles.
Measure angle DAB and angle BCD.
Angle DAB and BCD added up to 180 degrees proving they are
supplementary angles. Angle DAB is
1/2 of arc BCD and angle BCD is 1/2 of arc BAD. In conclusion anytime you have an inscribed quadrilateral,
(inside the circle), opposite angles will be supplemental.