Question

Name a interior angle and a exterior angle.

Answer 1

Interior: 6,3,5,4
Exterior: 1,2,8,7

Answer 2

Explanation:

Let L1 and L2 be parallel lines cut by a transversal T such that ∠1 and ∠3 are alternate interior angles. Let us prove that ∠1 ⩭ ∠3.

1. ∠1 ⩭ ∠2

1. PCA Postulate

2. ∠2 and ∠3 form vertical angles

2. Vertical Angles Definition

3. ∠2 ⩭ ∠3

3. Vertical Angle Theorem

4. ∠1 ⩭ ∠3

4. Transitive Property of Congruence

Let L1 and L2 be two lines cut by a transversal T such that ∠2 and ∠3 form congruent alternate interior angles as shown in the figure. Let us prove that L1 // L2.