Tutorial on angles formed when a transversal L3 intersects two parallel lines L1 and L2. You may also want to solve problems related to Parallel Lines and Angles.

Corresponding Angles All corresponding angles are congruent and are equal in measure. The pairs of angles a and a ' , b and b ' , c and c ' and d and d ' are corresponding angles.(see figure below). measure of angle a = measure of angle a ' measure of angle b = measure of angle b ' measure of angle c = measure of angle c ' measure of angle d = measure of angle d ' Alternate Interior Angles The pairs of alternate interior angles in the figure below are d and d ' and c and c '. The alternate interior angles are congruent and equal in measure. (see figure below) measure of angle d = measure of angle d ' measure of angle c = measure of angle c ' Alternate Exterior Angles The pairs of alternate exterior angles in the figure below are a and a ' and b and b '. The alternate exterior angles are congruent and equal in measure. See figure below) measure of angle a = measure of angle a ' measure of angle b = measure of angle b ' More References and Links to Geometry Geometry Tutorials, Problems and Interactive Applets.