1. The problem statement, all variables and given/known data A projectile is fired up an incline (incline angle φ) with an initial speed vi at an angle θi with respect to the horizontal (θi > φ). (a.) Show that the projectile travels a distance d up the incline, where d = 2*vi^2*cosθi*sin(θi-φ) / g*cos(φ)^2 (b.) For what value of θi is d a maximum, and what is the maximum value? 2. Relevant equations 3. The attempt at a solution Ok I am back and unbelievably got part a, but I have no idea how to do part b. I know 45 is the way to get maximum range, but I don't think that is the right angle, because we want to maximize x^2+y^2. Any help would be appreciated!