1. The problem statement, all variables and given/known data ball is thrown in angle α (balistically) from height H. Waht is the placement vector in any moment? 2. Relevant equations 3. The attempt at a solution Ok I know acceleration is: a(t) = (0,−g) it means the velocity is: v(t)=(v0 cosα , v0 sinα − gt) But the answer says the location vector is r(t) = v0 cosαt,H + v0sinαt-(0.5gt2)/2) shouldn't be: r(t) = -v0 sinαt,H + v0cosαt-(0.5gt2)/2) ? When I do it my way the other parts of the problem turns wrong since my rx got a minus ....then I get equation of the type x2=-t (for instance). And the answer should come with tanα since my cos and sin are different I get cot....I dun get why it comes wrong since even if I mistook the minus I know for sure cos=sin and sin=>cos I can;t integrate it leaving it as it was can it be there is a problem with the answer? They didn't say the angle was referring to speed but actually the curve the ball was thrown at... can I integrate without integrating the cos and sin?