 | Steradian (sr): multiples and submultiples |
 | symbol: sr
The steradian or square radian is the unit of solid angle in the International System of Units (SI). It is used in three-dimensional geometry, and is analogous to the radian, which quantifies planar angles. A steradian can be defined as the solid angle subtended at the centre of a unit sphere by a circular unit area on its surface. The solid angle is related to the area it cuts out of a sphere: Ω = (A / r2) * sr Ω is the solid angle A is the surface area of the spherical cap r is the radius of the sphere |
  
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 | solid angle |
measurement units | |
