Steradian and radians

We measure angles on paper, in two dimensions, in either degrees or radians but when we need to deal with three dimensions, for example when something spreads out like a cone, then the unit used is a steradian.

The video below illustrates and explains exactly what a steradian is.

Measuring solid angles

Radian

In more advanced physics and maths angles are frequently measured in radians rather than degrees. The video quickly explains what a radian is and how those units relate to degrees.

What is a radian