View source for Steradian

A unit of measurement of a [[Solid angle|solid angle]]. A steradian is the solid angle that cuts out on a sphere a surface described around the vertex of the angle of area equal to the square of the radius of the sphere. A complete sphere forms a solid angle equal to <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/s/s087/s087740/s0877401.png" />. Denoted by ster.