Short derivation of solid angle

[Hardik Batra]

I want to know the derivation of solid angle.

I have found on net. But the derivation is to long, is there any short method?

 

[Andy Resnick]

There are a few ways to define solid angle- square degrees or steradians.

http://en.wikipedia.org/wiki/Square_degree
http://en.wikipedia.org/wiki/Steradian

 

[Hardik Batra]

There are a few ways to define solid angle- square degrees or steradians.

http://en.wikipedia.org/wiki/Square_degree
http://en.wikipedia.org/wiki/Steradian

This link didn't give me derivation.