A.2 How do they differ?

Angles

Lines r and s are parallel. Alex finds the relationship between ∠1 & ∠5 and ∠2 & ∠6.

m∠1 = 120°
m∠6 = 60°
Alex's "Above the Line" Method
Because ∠1 and ∠2 are supplementary, I know that
180° - 120° = ∠2.
Because ∠5 and ∠6 are supplementary, I know that
180° - 60° = ∠5.
∠1 and ∠5 are both 120°, ∠2 and ∠6 are both 60°.
180° − 120° = 60°
180° − 60° = 120°
∠1 ≅ ∠5
∠2 ≅ ∠6