This sum is really wrecking my head. a satellite orbits the earth in a circular orbit, a height 'b' above the earth's surface. A missile is launched from the earths surface(in the satellites plane) with a speed V at an inclination theta to the vertical, and h= RVsin(theta) for the missile (R being the radius of the earth), we want the missile to hit the satellit at the apogee of the missiles elliptical orbit. The question wants me to prove that some massive equation holds, i amn't worried about that, what i AM really annoyed about is the vagueness of line 3 of the above paragraph. Surely why would my professer ask us to set up a vertical axis, when we can just have the velocity be 100% tangential and then we can assume perigee to be that position. Obviously i am reading it wrong, i don't want the answer to the problem, i just want to know what are they alluding to when they say that the missile is launched with a speed V AT AN ANGLE THETA TO THE VERTICAL? If the angular momentum is given by RVSin(theta) then our ellipse will NOT be working with the condition that the velocity at perigee, but VCos(theta). Am I wrong to assume this. I would appreciate it if anybody could clear up this mess. thanks.