We start with triangle ABC and see that angle ZAB is an exterior angle created by the extension of side AC. Angles ZAB and CAB are a linear pair by definition. We know that m∠ZAB + m∠CAB = 180° by the . We also know m∠CAB + m∠ACB + m∠CBA = 180° because . Using substitution, we have m∠ZAB + m∠CAB = m∠CAB + m∠ACB + m∠CBA. Therefore, we conclude m∠ZAB = m∠ACB + m∠CBA using the .
Answer
Selection 1:
angle addition postulate
Selection 2:
of the triangle angle sum theorem
Selection 3:
subtraction property

Question

We start with triangle ABC and see that angle ZAB is an exterior angle created by the extension of side AC. Angles ZAB and CAB are a linear pair by definition. We know that m∠ZAB + m∠CAB = 180° by the . We also know m∠CAB + m∠ACB + m∠CBA = 180° because . Using substitution, we have m∠ZAB + m∠CAB = m∠CAB + m∠ACB + m∠CBA. Therefore, we conclude m∠ZAB = m∠ACB + m∠CBA using the .

Answer

Selection 1:

angle addition postulate

Selection 2:

of the triangle angle sum theorem

Selection 3:

subtraction property

Revolt · Accepted Answer

angle addition postulate; Selection 1: angle addition postulate; Selection 2: of the triangle angle sum theorem; Selection 3: subtraction property