Lets say a Projectile is fired at an angle (theta) from the Horizontal. The Catch is that the place it was fired from is a hill sloped angle (phi) against the horizontal. The question is what are the angles are which you can get the highest Range (Range = not the Farthest Horizontal Distance, but the farthest distance along the slop). Hint: If (phi) is 60, then (theta) is 15. I've tried doing this problem multiple ways. I set the slope length as D. Making the Vertical displacement vector at the end -Dsign(phi), and the Horizontal Displacement Vector Dcos(phi). I then used the basic Kinematics equations and combined them. I solved for t under the horizontal displacement and plugged in what I got into my vertical displacement equation, but I keep going nowhere because I have a bunch of sines and cosines with theta and phi. Can anyone save me? I understand if the ground was flat, the answer would be 45 Degrees as the firing angle, but... with the slope it is VERY different.