So I was trying to compute the are of a sphere. There are many ways to do this like integrating small rings on the sphere etc. I was looking to do this using the notion of a solid angle.
What I know is that the surface element for a solid angle is
$dA = r^2 d\Omega$
I was wondering what to do further?
$\int dA = \int r^2 d\Omega$
What limits do I put in the above integral?