When a pair of parallel lines meet an intersecting transversal ... We've already seen that intersecting lines create vertically opposite angles that are equal. The lines make an X shape.

The diagonal line is a transversal as it is crossing the pair of parallel lines. When two lines intersect, the opposite angles are equal. Alternate angles are on opposite sides of the transversal ...

If two lines intersect each other, then the vertically opposite angles are equal. • If a transversal intersects two parallel lines, then (i) each pair of corresponding angles is equal ...