Proof: Collinear Angles Property 10
Let's prove the following theorem:
if m∠ABC = 180, then m∠XCB = m∠XCA
Proof:
Given
| 1 | m∠ABC = 180 |
|---|
| # | Claim | Reason |
|---|---|---|
| 1 | m∠BCX = m∠ACX | if m∠ABC = 180, then m∠BCX = m∠ACX |
| 2 | m∠BCX = m∠XCB | m∠BCX = m∠XCB |
| 3 | m∠ACX = m∠XCA | m∠ACX = m∠XCA |
| 4 | m∠XCB = m∠ACX | if m∠BCX = m∠XCB and m∠BCX = m∠ACX, then m∠XCB = m∠ACX |
| 5 | m∠XCB = m∠XCA | if m∠XCB = m∠ACX and m∠ACX = m∠XCA, then m∠XCB = m∠XCA |
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