Radian

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

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