Читать книгу Introduction to Desalination - Louis Theodore - Страница 41

Two supplementary units complement these seven primary units. They include:

1 Phase angle – radian (rad). The radian is the plane angle with its vertex at the center of a circle that is subtended by an arc equal in length to the radius.

2 Solid angle – steradian (sr). The steradian is the solid angle with its vertex at the center of a sphere that is subtended by an arc of the spherical surface equal to that with sides equal in length to the radius.