Question

Ethan is proving the Exterior Angle Theorem, which states that the measure of an exterior angle of a triangle is equal to the sum of the measures of the two remote interior angles.

Given: Triangle ABC on line segment AD

Prove: m∠ A + m∠ B = m∠ BCD

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What statement should Ethan add at Step 5 to complete the proof?
A. m∠ BCA+ m∠BCD = 90°

B. m∠ BCA= m∠BCD

C. m∠ BCA+ m∠BCD = 180°

D. m∠ BCA< m∠BCD

Answer 1

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