A transversal line is one that crosses two or more lines at different points.
Transversal Properties :
Each pair of corresponding angles when a transversal cuts two parallel lines are equal in size.
Each pair of alternate interior angles created by a transversal when two parallel lines are cut are equal.
If two parallel lines are cut by a transversal, then each pair of interior angles on the same side of the transversal are supplementary, i.e. they add up to 180 degrees
Each pair of corresponding angles when a transversal intersects two parallel lines is equal. Thus,
∠1 = ∠6
∠4 = ∠8
∠2 = ∠5
∠3 = ∠7
Each alternate interior angle pair is equal if a transversal intersects two parallel lines.