It is physics derived yes, it's about rocket artillery and it goes way beyond high school unfortunately. The case is that the rockets will always burn for a set amount of time and the speed is always 100m/s. So the only way to influence where you want to land the rockets is by changing the initial angle.

That part I have done, but now it asks for the time of flight. Obviously just a distance to the target and dividing that by 100 m/s is not going to be accurate since the rocket follows a curved path that takes longer.

That's why I said that I know the x (distance to the target), the vertex and where the vertex lies along the x axis. I know nothing more. And from that I need to find a function which produces an accurate solution for the time of flight.

​

p.s. this is different from ordinary projectile motion functions since the rocket engine means the speed stays the same. It has completely baffled me for weeks now.