1. The problem statement, all variables and given/known data The position of a particle at time t is given by r(t) = 3(t2 - sin t)i + tj - (cos t)k , and the position of another particle is R(t) = t2i + (t3 + t)j+(sin t)k . At time t = pi, what is the rate of change of the distance between the two particles? Are they getting closer to one another, or are they getting farther apart? 2. Relevant equations 3. The attempt at a solution I'm actually not sure how to attempt this problem. I think that if the rate of change is postive they are getting farther apart and if it is negative they are getting closer, but I'm not sure.