Radian

From Simple English Wikipedia, the free encyclopedia

This article's English may not be simple
The English used in this article may not be easy for everybody to understand.

You can help Wikipedia by making this page or section simpler.

Definition of Radian, where α is an angle and r is the radius.
Definition of Radian, where α is an angle and r is the radius.

A radian is a unit of measuring angles. It is shown by the symbol "rad" or, less often, c (for circular measure). The radian was once an SI unit, but was done away with in 1995.

[edit] Conversion

1 Radian is equal to about 57.2°. There are 6.28 (2π) radians in a full circle. The formula for turning radians to degrees and vice versa is:

2\pi\mbox{ rad} = 360^\circ
1 \mbox{ rad} = \frac {360^\circ} {2 \pi} = \frac {180^\circ} {\pi} \approx 57.29577951^\circ

or:

360^\circ=2\pi\mbox{ rad}
1^\circ=\frac{2\pi}{360}\mbox{ rad}=\frac{\pi}{180}\mbox{ rad} \approx 0.01745329\mbox{ rad}

we can also say:


x \mbox{ rad} = x \frac {180^\circ} {\pi}.