Try it Proving the sum of the Interior Angle Measures of a
Triangle Is 180°
Given: y || z
Prove: m25+ m2 2 + m26 = 180°
Angige Lines Statements Reasons
21
23
11
25
26
m21
m23
m25
m 26
!
A
M
1
1
2
y
Reasons
2 alternate interior angles theorem
3. def. of
4. angle addition postulate
4/5
С
6 72
B
Statements
2. 21-25
3. mZ1 = m25
4. mZ1+ m2 2 + m2 3 =
mZLAM
5. m21+ m2 2 + m 23 = 180
6. 232 26
✓ 7. m3 = m26
8. m25+ m2 2 + m 26 = 180
5. def. of straight angle
6. alternate interior angles theorem
7. def. of
8. substitution
Correct! You have completed this
exercise