D
B
G
A
E
C
F
In the figure above, DE is parallel to GF . Find a way to prove that the angles in ABC
have a sum of 180.




D
B
G
A
E
C
F
In the figure above, DE is parallel to GF . Find a way to prove that the angles in ABC
have a sum of 180.




Statement
Reason
1. Given
1.
2. Alternate Interior Angles Theorem
2.
3.
3. Reflexive Property of Congruence
4.
4. Definition of Congruency
5.
is a straight angle
5. Picture
6.
6. Definition of a Straight Angle
7.
7. Angle Addition Postulate
8.
8. Substitution