Given: In circle O, arc AB = arc CD, OP ⟂ AB, and OQ ⟂ CD

Prove: AP = CQ

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Substitution
Definition
If a diameter is perpendicular to a chord, it bisects the chord
Algebra
AP = CQ
Substitution
Equal arcs have equal chords
OP bisects AB and OQ bisects CD
AB = AP + PB and CD = CQ + QD
AP + PB = CQ + QD
OP ⟂ AB and OQ ⟂ CD
AP + AP = CQ + CQ
AP = PB and CQ = QD
AB = CD
Given
Segment addition theorem