posted by Pat .
A football player punts the football so that it will have a hang time of 4.5s and land 46m away. If the ball leaves the player's foot 1.5m above the ground, what must be (a) the magnitude and (b) angle (relative to the horizontal) of the ball's initial velocity?
that is the first equation, solve for vi in terms of all else.
put the Vi you got above, put it in, and solve for theta (you should have a tanTheta=xxxx)