Encyclopedia > Radian

  Article Content


The radian is the SI supplementary unit of angle. It is defined as the angle subtended at the center of a circle by an arc of circumference equal in length to the radius of the circle.

There are 2π (about 6.283185) radians in a complete circle. One radian is equal to 180o/π or approximately 57.29578o.

In calculus, the use of radians leads to the simple identity

<math>\lim_{h\rightarrow 0}\frac{\sin h}{h}=1</math>
which is the basis of many elegant identities in mathematics.

For measuring solid angles, see steradian.

All Wikipedia text is available under the terms of the GNU Free Documentation License

  Search Encyclopedia

Search over one million articles, find something about almost anything!
  Featured Article

... simplicity of Copernicus' cosmology and much of this seeming simplicity resulted from his retention of circular orbits for the planets around the central Sun. Not that ...