# Solid angle and plane

1. Dec 23, 2013

### Jhenrique

Hellow!!!

I known an infinitesimal relation between the solid angle Î© with the azimutal angle Î¸ and zenital Ï†, that's given by dÂ²Î© = sin(Ï†) dÏ† dÎ¸. But this is infinitesimal relation, exist other relation non infinitesimal between the solind angle with the plane angles? Thanks!

2. Dec 23, 2013

### tiny-tim

Hello Jhenrique!

Solid angle is the same as area (on a unit sphere), for which there are standard formulas.

In particular, if you know all three angles of a triangle, the area is their sum minus Ï€.

(i don't remember the other formulas, but a quick google search will find them )

3. Dec 23, 2013

### Jhenrique

I found nothing more. I thought if an area can have 2 definitions A = xy and dA = dxdy, then the solid angle could have 2 definitions too, 1 algebric definition and 1 infinitesimal definition...