Alternate Interior Angles Theorem

When It's Used:The Alternate Inerior Angle Theorem is used to find the measure of an angle between two parallel lines, provided that the angle in question is on the opposite side of the intersecting transversal than a known angle. The converse of this theorem can be used to find if two lines are parallel provided that there are two equal angles on opposite sides of an intersecting transversal between the two lines.

Alternate Interior Angles Theorem

Definition:-If a transversal intersects two parallel lines, then the alternate interior angles are congruent.-The converse is also true.