Proving the Sum of the Interior Angle Measures of a Triangle Is 180°
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Given y || z
Prove: m25+ m22 + m26 = 180°
Angles Lines Statements Reasons
def. of
def of straight angle
angle addition postulate
alternate interior angles theorem
A
M
2
3
Statements
✓ 1.3 112
2.2125
Reasons
1. given
2. alternate interior angles theorem
4
5
6 7 z
B
С
Look for alternate interior angles