Types of Angles

This page will include information on various types of angles including complementary, supplementary, vertical, interior, exterior, and corresponding angles.

Acute, Obtuse, and Right Angles

An acute angle consists of less than 90 degrees. (A)

An obtuse angle consists of more than 90 degrees. (C)

A right angles consists of 90 degrees. (B)

Complementary Angles

Two angles are complementary if the sum of their degree equals 90 degrees.

58 + 32 = 90 so the angles are complementary

They form a right angle when set adjacent to each other

Supplementary Angles

Two angles whose measures add up to 180 degrees are supplementary angles.

139 + 41 =180 so the angles are supplementary

When set adjacent to each other they form a strait line

Vertical Angles

When two lines intersect, the angles across from each other are vertical angles. Vertical angles also have the same measurement.

Angles A and B are vertical angles so they have the same angle measure. The same is true of angles C and D.

Alternate Interior Angles

Alternate interior angles are created when a line is intersected by two parallel lines as shown below. Alternate interior angles have equal measures.

Angles A and D are alternate interior angles and therefore have the same measure. The same is true of angles B and C.

Alternate Exterior Angles

Just like alternate interior angles, these angles are formed when parallel lines intersect a line. Alternate exterior angles are simply the angles on the outside  (exterior).

Angles A and D are alternate interior angles, as are angles B and C.

Corresponding Angles

In addition to alternate interior and exterior angles, when parallel lines intersect a third line corresponding angles also exist. Corresponding angles are simply angles that are in similar positions around the intersection. They have the same angle measure.

Angles A and C are corresponding angles, and so are angles B and D.