How Do You Determine Forces in a Truss Structure?

[rikka22]

Homework Statement

Determine the forces in each member of the truss shown. Also find the values for any reactant forces

http://img201.imageshack.us/img201/6853/trussnu9.jpg

Homework Equations

F_x= 0
F_y= 0

The Attempt at a Solution

I set θ in the corner of J₁
tan θ=12/16
θ = tan^-1 12/16
θ = 36.87

I set Φ in the corner of J₃
tan Φ = 12/9
Φ = tan^-1 12/9
Φ = 53.13

This is where I began to falter. I could not figure out how to diagram everything out. If someone could just at least give me a diagram of where things are supposed to go, I can sum up the x and y forces by myself. This is pretty urgent, and I was absent for this class so my only help is messy notes from another student. This isn't in my textbook. Any help will be appreciated.

 

[chaoseverlasting]

You want to resolve the forces. If a force F makes an angle \theta with the horizontal, the horizontal force is F_x=Fcos\theta and the vertical force is F_y=Fsin\theta.

Give us something to work on and we'll lead you on.