Two angles that have the same measure.
Angles are denoted by three letters, with the vertex letter in the middle. For example, angle AOB is written as ∠AOB.
Congruent angles are symbolized by the ≅ symbol. For example, ∠AOB≅∠COB means that angle AOB is congruent to angle COB.
Congruent angles have the same measure and orientation, and the same corresponding sides.
To find congruent angles, look for vertical angles, corresponding angles, or alternate interior angles.
In the following diagram, ∠AOB≅∠COD because they are corresponding angles.
In the following diagram, ∠AOB≅∠COD because they are alternate interior angles.