1. The problem statement, all variables and given/known data i want to prove that the functions u(r,t)=(1/r)f(r-v*t) and u(r,t)=(1/r)f(r+v*t) satisfy the wave equation in spherical coordinates, i have tried a lot to solve it but in each time i would face a problem. 2. Relevant equations wave equation : grad^2(u)=(1/v)*(partial ^2 u/partial t ^2) 3. The attempt at a solution i have tried to solve it in different ways but it does not work with me.