Proof: Right Angle in Equilateral
Let's prove the following theorem:
if △XYZ is an equilateral triangle and M is the midpoint of line XY, then ∠XMZ is a right angle
Proof:
Given
| 1 | △XYZ is an equilateral triangle |
|---|---|
| 2 | M is the midpoint of line XY |
| # | Claim | Reason |
|---|---|---|
| 1 | distance XZ = distance YZ | if △XYZ is an equilateral triangle, then distance XZ = distance YZ |
| 2 | m∠XMZ = 90 | if distance XZ = distance YZ and M is the midpoint of line XY, then m∠XMZ = 90 |
| 3 | ∠XMZ is a right angle | if m∠XMZ = 90, then ∠XMZ is a right angle |
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