1. The problem statement, all variables and given/known data http://session.masteringengineering.com/problemAsset/1127430/5/Probs.2-83_84.jpg Refer to image for problem. I have to find the magnitude of the force F3. I'm stuck on where to begin. 2. Relevant equations Don't know. 3. The attempt at a solution I've done. cos(y)=sqrt(1-cos^2(60)-cos^2(45)) I got the y angle to be 60. I don't know what that means so if someone could explain that would be great. I just used this because I thought I needed to know that. I then tried to break down each force vector into their components. F = x, y, z F1=80(4/5), 0, 80(3/5) F2=0, 0, -110 F3=? FR=120cos(60), 120cos(60), 120cos(45) Thats all I got. I don't know what to do now.