Question

Proving the alternate exterior angle theorem.

https://media.studyisland.com/pics/38507four.png

Given: f g and line d is a transversal.

Prove: 1 8

Proof:

1. Line f is parallel to line g.
Line d is a transversal. given
2. 1 5. If parallel lines are cut by a transversal,
then corresponding angles are congruent.
3. 5 8. vertical angles are congruent
4. 1 8.

Which of the following reasons completes the proof?
transitive property of congruence
reflexive property of congruence
alternate interior angles are congruent
symmetric property of congruence