Given: ZAOB is a central angle and ZACB is a circumscribed angle. Prove: AACO ABCO A O We are given that angle AOB is a central angle of circle O and that angle ACB is a circumscribed angle of circle O. We see that AOBO because We also know that ACC since Using the reflexive property, we see that Therefore, we conclude that AACO is congruent to ABCO by the B