Use the vertical angles theorem to name a pair of congruent angles

If we have two parallel line cut by a transversal such that the number of the angles are ordered in this manner:

1 | 2

3 | 4

5 | 6

7 | 8

The following the pair of vertical angles

∠1 and ∠4

∠2 and ∠3

∠5 and ∠6

∠7 and ∠8