1. The problem statement, all variables and given/known data Calculate the average vector velocity between 0 and pi/4 sec. 2. Relevant equations x=rcos2t y=rsin2t Vx=2rsin(2t) Vy=2rcos2t Ax=4rcos(2t) Ay=-4cos(2t) Circular path is x^2+y^2+r^2 3. The attempt at a solution I'm not sure if I am missing something simple or not, What I need to know is what is r and so I initially set the square of the x and the square of the y equations equal to the square r. Pythagorean style. when I solved for r I felt just a little dumb because I got 1=1 which well duh I shoul've saw that coming. Now I'm trying to guess whether I even need r to do an average, or if there is another way to solve for r that I am missing. I also know that x=r when t=0 but when I sub r for x in the position equation I just get 1.