Introduction to Angles Basic terms related to the classification of angles. Tools A B Right Angle An angle that measures exactly 90 degrees Straight Angle An angle that measures exactly 180 degrees Acute Angle An angle that measures less than 90 degrees Obtuse Angle An angle that measures between 90 and 180 degrees Congruent Angles Two angles that have the same measure Vertex The endpoint where two rays meet, forming an angle Bisect To separate an angle into two congruent angles Degrees The unit that angles are measured by