# Differentiating the following average.

I am trying to find $\frac{\partial ^2}{\partial r^2} \frac{1}{|\partial B(x,r)|} \int_{\partial B(x,r)} u(y,t)\mathrm{d}y$ . Where $B$ is a ball of radius $r$ with center at $x$ .

Differentiating once was ok , but i couldn't not again differentiate .

Thank you for your help .

• What's "average" doing in there? Jul 10, 2012 at 10:40
• @joriki : I don't know how to make it $\int$ with the cut , ie average of surface integral . Jul 10, 2012 at 10:42
• AFAIK the \strokedint or \fint commands are not implemented in MathJax, so I just replaced it by the definition. Jul 10, 2012 at 11:02
• @WillieWong : Thank you . Jul 10, 2012 at 11:06