Conduction through a hollow sphere

yanks28247

Hi, I'm stuck on this derivation:

Derive an equation which shows that the temperature varies hyperbolically with the radius r for steady-state conduction of heat in a hollow sphere.

I know the answer is:

(T-T1)/(T2-T1) = (r2/(r2-r1))(1-(r1-r))

But how do you get it?

I also know that q = (T1-T2)/((1/r1-1/r2)/(4pik))

Thanks