Basically need to use einstein's summation convention to find the grad of (mod r)^n and a.r where a is a vector and r = (x,y,z)
The Attempt at a Solution
Not sure where to begin really.. :S
grad (mod r)^n= (d/dx, d/dy, d/dz) of root (X1^2 + x2^2 + x3^2)^n..
Just not sure what to do now..