I posted the following problem a few days ago: So it's about somebody on a bike who rides off an entrenchment (that's what it's called right?) with a velocity v under an angle of alpha with the ground. He's hoping to land safely on another entrenchement that's h heigher than the first one, at a distance x from the first entrenchment: http://img372.imageshack.us/img372/8958/projectilemotion3gj.gif [Broken] For a given height h, I found the minimal velocity vmin the jumper needs to have in order to land safely on the platform at a distance x: v0= (x/cos@) sqrt(g/2(x tan @ -h)) But how can I show that no matter what his takeoff speed is, the maximum height of the platform is hmax < x tan @. I need to interpret this result physically. Well I don't know how to do the last thing, because I know that is hmax < x tan @ the argument under the sqrt will be negative and therefore out of the domain of the sqrt function... I don't see the physical consequences... Could someone please help me?