To complete the proof that consecutive interior angles are supplementary, the correct statement to insert for reason 2 is:
Transitive Property of Equality
This is because if m∡A = m∡E (statement 2), and we already know from step 1 that m∡A + m∡C = 180° (which implies that m∡E + m∡C = 180° through the transitive property), it logically connects the two equations.
So, the completed proof would read:
- m∡A + m∡C = 180°
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- Linear Pairs are supplementary
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- m∡A = m∡E
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- Transitive Property of Equality
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- m∡E + m∡C = 180°
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- Substitution
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- ∠E and ∠C are supplementary
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- Definition of Supplementary Angles
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Thus, the correct choice is Transitive Property of Equality.