Why Does the Cylindrical Wall Heat Equation Solution Include Logarithms?

[clava345]

I'm a little bit rusty with my differential equations, and can't seem to see how solving for 1/r d/dr (r dT/dr)=0 has the solution T(r)=C_1*ln⁡(r)+C_2

 

[JJacquelin]

integration of d/dr (r dT/dr)=0 leads to (r dT/dr) = C1
dT = C1 dr/r
integration of dT=C1 dr/r leads to t = C1 ln(r) + C2

 

[clava345]

Thanks