Proof: Exterior Angle Other
Let's prove the following theorem:
if m∠XZE = 180, then m∠YZE > m∠YXZ
Proof:
Given
Assumptions
1 | m∠XZE = 180 |
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2 | M is the midpoint of line XZ |
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3 | M is the midpoint of line YG |
4 | m∠YZF = 180 |
5 | m∠FZG > 0 |
# | Claim | Reason |
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1 | distance XM = distance MZ | if M is the midpoint of line XZ, then distance XM = distance MZ |
2 | distance ZM = distance XM | if distance XM = distance MZ, then distance ZM = distance XM |
3 | distance YM = distance MG | if M is the midpoint of line YG, then distance YM = distance MG |
4 | distance MG = distance MY | if distance YM = distance MG, then distance MG = distance MY |
5 | m∠YMG = 180 | if M is the midpoint of line YG, then m∠YMG = 180 |
6 | m∠XMZ = 180 | if M is the midpoint of line XZ, then m∠XMZ = 180 |
7 | m∠ZMG = m∠XMY | if m∠XMZ = 180 and m∠YMG = 180, then m∠ZMG = m∠XMY |
8 | △ZMG ≅ △XMY | if distance ZM = distance XM and m∠ZMG = m∠XMY and distance MG = distance MY, then △ZMG ≅ △XMY |
9 | m∠GZM = m∠YXM | if △ZMG ≅ △XMY, then m∠GZM = m∠YXM |
10 | m∠GZM = m∠GZX | if m∠XMZ = 180, then m∠GZM = m∠GZX |
11 | point M is in segment XZ | if M is the midpoint of line XZ, then point M is in segment XZ |
12 | point G lies in interior of ∠XZF | if point M is in segment XZ and m∠YMG = 180 and m∠YZF = 180, then point G lies in interior of ∠XZF |
13 | m∠XZF = (m∠XZG) + (m∠GZF) | if point G lies in interior of ∠XZF, then m∠XZF = (m∠XZG) + (m∠GZF) |
14 | m∠FZX = (m∠FZG) + (m∠GZX) | if m∠XZF = (m∠XZG) + (m∠GZF), then m∠FZX = (m∠FZG) + (m∠GZX) |
15 | m∠FZX > m∠GZX | if m∠FZX = (m∠FZG) + (m∠GZX) and m∠FZG > 0, then m∠FZX > m∠GZX |
16 | m∠FZX = m∠YZE | if m∠YZF = 180 and m∠XZE = 180, then m∠FZX = m∠YZE |
17 | m∠YZE > m∠GZX | if m∠FZX > m∠GZX and m∠FZX = m∠YZE, then m∠YZE > m∠GZX |
18 | m∠GZX = m∠YXM | if m∠GZM = m∠GZX and m∠GZM = m∠YXM, then m∠GZX = m∠YXM |
19 | m∠YZE > m∠YXM | if m∠YZE > m∠GZX and m∠GZX = m∠YXM, then m∠YZE > m∠YXM |
20 | m∠YXM = m∠YXZ | if m∠XMZ = 180, then m∠YXM = m∠YXZ |
21 | m∠YZE > m∠YXZ | if m∠YZE > m∠YXM and m∠YXM = m∠YXZ, then m∠YZE > m∠YXZ |
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