The coordinate of a boy running across a parking lot as a function of time is gives as :x�0†3=3t*2 7.2t 28 and y�0†3=0.28t*2 - 9.1t 30...express the boys position vector r�0†3 and velocity v�0†3 in unit vector rotation and find the magnitude and angle at time 20s
I'm lost on your notation but...
Position is simply (3t^2 + 7.2t + 28)i +(.28t^2 - 9.1t +30)j
v = dx/dt:
(6t + 7.2)i + (.56t - 9.1)j
Magnitude of WHICH angle?
tan-1(j component @ 20 / i component @ 20)