3d vector tension problem!!!

[arpitm08]

1. The problem statement, all variables and given/known data
A traffic light with a mass of 20kg hangs from 3 wires, each of length 15 meters. The wire are at right angles to each other and the light hangs below the point of attachment to the three wires and is a position symmetric to the wires. What is the magnitude of the tension (force) on each wire?


2. Relevant equations
I don't know.


3. The attempt at a solution
I haven't taken physics yet, so i don't know about tension force that much. I know that it has something to do with 3d vectors, because thats the chapter we are in right now. If someone could give me something to start on that would be great.

[HallsofIvy]

I don't see how you can do this with out know HOW far below the point of attachement the light is.

[arpitm08]

My teacher explained it to us now. Its easy once you realize that the 90 degree angles mean that it is the 3d coordinate axis. Then the resultant tension force is sqrt(3)T, where T is the tension in each string. Then you set that equal to 20g and you solve for T.