All right, before I look like a big idiot, I want to preface this with a statement that I have been through Cal III, Abstract Algebra, I'm a senior in college, and I got a 620 on the math portion of the SAT. And I CANNOT get this basic problem in projectile motion figured out. Physics has humbled me. Anyone that understands physics gets my highest regard after just getting to the third chapter in this algebra-based physics book. Here's my problem: We've got a football being thrown at an undetermined angle, theta, at 20m/s. It lands (at the same height, for the sake of ease) 25 meters away. I know that we know Xnaught, X, Vnaught, asuby, ynaught and y. So I start trying to set the problem up and come up with: x=-2VoxVoy/ay I know that the Vnaughtx (which I can't type, since it looks dirty ) is basically the velocity (20 m/s) times the cosine of the angle of release. Vnaughty ( ) is the same, but with sine, right? Okay, so I solve down algebraicially to (xay)/(-2v^2) = cos(theta) sin(theta) And I've got nowhere to go after that. I got nothin'. I checked out the trig identities, thinking that might be the equivalent of Tangent, but it's not. Am I using the wrong equation? Thanks in advance for anyone who can help me not fail this class.