Vertical angles are congruent.
Alternate interior angles are
pairs of angles whose interiors lie between the parallel
lines, but on opposite sides of the transversal. Alternate
interior angles are congruent.
Alternate exterior angles are
pairs of angles that lie outside the parallel lines,
but on opposite sides of the transversal. Alternate
exterior angles are congruent.
Corresponding angles are two
nonadjacent angles whose interiors lie on the same side
of the transversal such that one angle lies between
the parallel lines and the other does not. Corresponding
angles are congruent.