How do you determine 'r' in Torque calculations?

[PhizKid]

Homework Statement

Homework Equations

Torque = r * F * sin(x)

The Attempt at a Solution

The solution says that the 'R' I marked was L*cos(phi). I fail to see the geometry of how they got this...you have only one side and one right angle for that triangle...how can you solve for 'R'?

 

[Doc Al]

you have only one side and one right angle for that triangle...

You should be able to find the other angles, for example between the right hand rope and the bar.