Alternate Interior Angles
In
the drawing below, angles 3 and 6 are alternate interior angles,
as are angles 4 and 5. Alternate interior angles are congruent.
Formally, alternate interior angles are two interior
angles which lie on different parallel
lines and on opposite sides of
a
transversal.
Parallel lines cut
by a transversal 

See
also
Alternate
exterior angles, consecutive interior angles
