Question

The position of a particle at time t is given by r(t)=3(t^2-sin(t))i+tj-(cos(t))k, and the position of another particle is R(t)=t^2i+(t^3+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?