Given: quadrilateral abcd is inscribed in circle o. prove: m∠a+m∠c=180° a quadrilateral is inscribed in a circle o. the vertices of the quadrilateral lie on the edge of the circle and are labeled as a, b, c, and d. drag an expression or phrase to each box to complete the proof. statements reasons quadrilateral abcd is inscribed in circle o. given inscribed angle theorem mdab=2(m∠c) mbcd+mdab=360° the sum of arcs that make a circle is 360°. substitution property m∠a+m∠c=180°