# Angle Definition and Properties of Angles

**angle**is a shape formed by two rays that have a common endpoint. In Trigonometry an angle is in

*standard position*if one ray is on the positive x axis (called the initial side) and the vertex is at the origin. The space between the two rays can be measured in either

*degrees or radians*. The terminal side can be rotated either counterclockwise or clockwise.

The angle can be named in two ways: (1) if there is only one angle the vertex can be used. For example: ∠B. (2) If there are multiple angles it is best to use three points. For example: ∠ABC using the vertex as the center letter. m∠B=45° means the measure of angle B is 45 degrees.

When rotating the terminal side

**the angle measure is**

*counterclockwise***. One full rotation beginning from the initial side is 360°. However, the terminal side can rotate numerous times creating very large angles. For example 720° would be two complete revolutions.**

*positive*When rotating the terminal side

**angles are created. One full rotation beginning from the initial side is -360° (negative 360°). The terminal side can be rotated numerous times creating large negative numbers. For example if the terminal side rotated 3 times the degree measure would be 1080°.**

*clockwise negative*
Related Links:Math Trigonometry Introduction to the Six Trigonometric Functions (Ratios) Standard Position of an Angle - Initial Side - Terminal Side |

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