Question

In circle O, chords AC and BD intersect at E. If MCD= 120 and MAB=100, what is BEC?

Answer 1

• D. 70°

Explanation:

∠BEC is supplementary with ∠BEA

Find the measure of ∠BEA

• m∠BEA = 1/2(mCD + mAB)
• m∠BEA = 1/2(120° + 100°) = 110°

Supplementary angles sum to 180°

• m∠BEC + m∠BEA = 180°
• m∠BEC = 180° - 110° = 70°

Correct choice is D