Given: ABCD is an inscribed polygon. Prove: ∠A and ∠C are supplementary angles. Drag an expression or phrase to each box to complete the proof. ABCD is an inscribed polygon.==Given. mBCD=2(m∠A)==Inscribed Angle Theorem. mDAB=2(m∠C)==_. mBCD+mDAB=360°==_. 2(m∠A)+2(m∠C)=360°==Substitution Property. m∠A+m∠C=180°==_. ∠A and ∠C are supplementary angles.==_. =Chord Arc Theorem, In scribed Angle Theorem, Central Angle Theorem, Subtraction Property of Equality, Division Property of Equality, Definition of supplementary Angles, The sum of arcs that make a circle is 360