﻿ Radian: An angular measure of rotation where one full circle equals 2*pi radians.

Pronunciation: /ˈreɪ diən/ ?

 Sorry, the GeoGebra Applet could not be started. Please make sure that Java 1.4.2 (or later) is installed and active in your browser (Click here to install Java now) Manipulative 1: Radian measure. Click on the blue point in the manipulative and drag it to change the figure.

A radian is a unit of measure for rotation around a point. 2π radians is the same rotation as one complete rotation about a circle. The abbreviation for radians is rad.

### Common angles in radians and degrees

Full circle
0 rad.none of a full circle
30° rad. of a full circle
45° rad. of a full circle
60° rad. of a full circle
90° rad. of a full circle
180°π rad. of a full circle
270° rad. of a full circle
Table 1: Common angles in radians and degrees

### How to convert radians to degrees

One complete rotation about a circle is 2π rad. or 360°. This means 2π rad. = 360°. So, the conversion factor is . Example: Convert radians to degrees.

### How to convert degrees to radians

The conversion factor for degrees to radians is . Example: Convert 45° to radians. .

• McAdams, David. Angle. allmathwords.org. Life is a Story Problem LLC. 2009-03-12. http://www.allmathwords.org/article.aspx?lang=en&id=Angle.

Radian. 2010-12-06. All Math Words Encyclopedia. Life is a Story Problem LLC. http://www.allmathwords.org/en/r/radian.html.