Inscribed Quadrilateral

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.