How to solve a prrof

Question

Given: Segment AB is parallel to segment CD

Prove: Arc of mAC = arc of mBD

Please help!

Answer 1

We assume that AB and CD are chords of circle O and that these chords are parallel.

 

Draw AD, a transversal that creates congruent angles BAD and CDA (alternate interior angles).

 

Arcs AC and BD each measure twice the measure of these congruent inscribed angles. Thus the arcs have equal measures.