1. The problem statement, all variables and given/known data How does one get the r" equation from r'? 2. Relevant equations r = distance v = r' = ds/dt a = r'' = dv/dt chain rule, dy/dt = dy/dx * dx/dt 3. The attempt at a solution I can easily get to r' from r using the chain rule but how do you derive r" from r'? How do you apply the chain rule when there are 3 variables (sec theta, tan theta and theta dot)? Help would be appreciated.