Hello, I am having an awfully hard time working out this rocket problem. Say you want to have a 2D representation of a rocket launching from the earth, either it will crash right away, have a decaying orbit or a stable orbit. If you launch a rocket at, say, 88 degrees it will have a velocity in the r-hat and phi-hat direction. It will continue to go higher and faster as the rocket consumes its fuel. To plot this using cylindrical coordinates, we need to know phi as a function of time. But how can one do this? The only way Iv thought how to do this is calculate the angle phi incrementally examining the triangles from one position to the next. Perhaps there is a better idea?