Angles are congruent if they have the same angle measure in degrees. They can be at any orientation on the plane. In the figure above, there are two congruent angles. Note they are pointing in different directions. If you drag any of the endpoints, the other angle will change to remain congruent with the one you are changing.

For angles, 'congruent' is similar to saying 'equals'. You could say "the measure of angle A is equal to the measure of angle B". But in geometry, the correct way to say it is "angles A and B are congruent".

To be congruent the only requirement is that the angle measure be the same, the length of the two arms making up the angle is irrelevant. As you drag the orange dots above, note how the line lengths will vary but the angles remain congruent, because only the angle measure in degrees matters..

Constructing congruent angles

Related topics

• Congruence defined
• Congruent lines
• Congruent angles

Congruent Triangles

• Congruent triangles
• Tests for congruence
  • 3 sides (SSS)
  • Side-Angle-Side (SAS)
  • Angle-Side-Angle (ASA)
  • Angle-Angle-Side (AAS)
  • Hypotenuse-leg (HL)
• Why AAA (angle-angle-angle) doesn't work
• Why SSA (side-side-angle) doesn't work

Congruent Polygons

• Congruent polygons
• Tests for polygon congruence