If you split the projectile in half so that you have a triangle approximation with base 18 and height 18tan30 then you can use V(vertical)=0 as at the top its a turning point for vertical velocity. Using v^2 =u^2 +2as its possible to obtain u(initial vert. comp.) Boils down to u=sqrt(-2as) s=18tan30, a=-9.81m/s/s, v=0m/s, u=_(rearrangement of the above) initial velocity = u(vertical)/ cos30 Its been a while since I'v done that stuff , so it could be complete rubbish.