Alternate Interior Angles Theorem (Converse)
if WX || YZ and m∠WSX = 180 and m∠YTZ = 180, then m∠WST = m∠STZ
This is a proof by contradiction
Given(s)
- WX || YZ
- m∠WSX = 180
- m∠YTZ = 180
Contradiction
Assumption
Assumptions
1 | m∠YTZ = 180 |
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2 | m∠HST = m∠STZ |
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3 | m∠HSI = 180 |
4 | line HI intersects line WX at point S |
# | Claim | Reason |
---|---|---|
1 | HI || YZ | if m∠HSI = 180 and m∠YTZ = 180 and m∠HST = m∠STZ, then HI || YZ |
2 | line WX intersects line YZ at point X | if HI || YZ and line HI intersects line WX at point S, then line WX intersects line YZ at point X |
The last statement (line WX intersects line YZ at point X) contradicts a given statement
Conclusion
m∠WST = m∠STZ
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