1. The problem statement, all variables and given/known data Engineers perform a crash test with a minivan and a compact car. The mass of the minivan is 800kg and the mass of the compact car is 560kg. The minivan was moving north, and the compact was was moving east. After the collision, the two cars crumpled together and moved at 15m/s [N 30 E]. Determine the initial velocity of each vehicle 2. Relevant equations P = mv 3. The attempt at a solution Okay so its inelastic: Minivan is 1 Compact car is 2 x: m1v1 + m2v2 = mtvf m2v2 = mtvf 560 * v2 = (560+800)(15*cos70) v2 = 12.45 m/s [E] y: m1v1 + m2v2 = mtvf 800*v2 = (560+800)(15*sin70) v2 = 24 m/s [N] The confusion is that these answers are wrong. The book gets completely different answers, and I've discovered its because the book does it like this How the book is doing it x: m1v1 + m2v2 = mtvf m2v2 = mtvf 560 * v2 = (560+800)(15*sin30) v2 = 18 m/s [E] y: m1v1 + m2v2 = mtvf 800*v2 = (560+800)(15*cos30) v2 = 22 m/s [N] This is so confusing for me. Why is the book using sin30 where I use cos70, and why is the book using cos30 where I am using sin70? I drew the triangle, and I just can't understand why the book is doing it like this. Can someone clear this up? Thanks I realize this is a trigonometry question. But why isn't sin70 equal to cos30 in the triangle I am drawing? Whats going on?