# Angle definition

Description of angles definition and relationships

## Angle definition

An angle is a figure formed by two rays that have the same endpoint. The common endpoint is the vertex of the angle.

• An angle that measures greater than 0 °, but less than 90 ° ist, is an acute angle

• An angle that measures greater than 90 °, but less than 180 ° is an obtuse angle

• An angle that measures 90 ° is a right angle

• An angle that measures 180 ° is a straight angle

to determine an angle measure in degrees, you can use a protractor. The mathematical symbol to indicate a degree measure is °. ## Winkelbeziehungen

Certain pairs of angles have special relationships. These relationships are useful in determining unknown angle measures. The following sections discuss some of these angle pair relationships.

• When the sum of the measurements of two angles equals 90 ° the angles are considered complementary.

• When the sum of two angles is 180 °, the two angles are considered supplementary.

• Two angles that have a common vertex and a common side are adjacent angles