vertical angles 2 and 5, 1 and 6, 3 and 8, 7 and 4
linear pair 1 and 5, 5 and 6, 6 and 2, 2 and 1, and also 3 and 7, 7 and 8, 8 and 4, 4 and 3
congruent angles - all vertical pairs are congruent angles
2 congruent to 5, 1 congruent to 6, 3 congruent to 8, 7 congruent to 4
