Proof: Supplementary Then 180

Let's prove the following theorem:

if ∠ABC and ∠DEF are supplementary, then (m∠ABC) + (m∠FED) = 180

C A B D E F

Proof:

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Given
1 ∠ABC and ∠DEF are supplementary
Proof Table
# Claim Reason
1 (m∠ABC) + (m∠DEF) = 180 if ∠ABC and ∠DEF are supplementary, then (m∠ABC) + (m∠DEF) = 180
2 m∠DEF = m∠FED m∠DEF = m∠FED
3 (m∠ABC) + (m∠FED) = 180 if (m∠ABC) + (m∠DEF) = 180 and m∠DEF = m∠FED, then (m∠ABC) + (m∠FED) = 180

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