So it is my understanding from my book that the information that we can get from a trajectory graph is the direction of velocity, but not the magnitude of velocity. If the tangent line to a point on a trajectory graph just gives the direction of velocity, why can the trajectory graph still be used to find instantaneous acceleration? Or is the acceleration we find with the trajectory graph just the rate of change of the direction of velocity instead of the rate of change in the magnitude of velocity? My main problem is just understanding how ax, ay, a, v, vx, and vy are related to a trajectory graph. I guess I just can't wrap my head around it because I think that we should only be able to find these values from a position vs. time graph.