Corresponding angles are equal. The lines make an F shape. Notice that the F shape can be upside down or back to front. We've already seen that intersecting lines create vertically opposite angles ...

This theorem dictates that vertically orientated ... as the concept of the corresponding angle, except that the bisecting ray will construct congruent angles on opposite corners of the transversal ...

When two lines intersect, the opposite ... looking for alternate angles, it can be helpful to look for a Z-shape. The Z-shape can be backwards, sideways or upside down. Corresponding angles ...