Solving an Electrostatics Problem with Two 5g Spheres

[antiflag403]

Hey everyone,
I'm not sure if this question warrants the "advanced physics" forums, but it would be nice if some of you smart people could give me a hand with this problem.
Two 5g spheres are charged to +100nC and hung from 1m long strings. What is the angle produced due to the repusive force.
So... I drew a free body diagram of the situation and realize that the net force is going to be 0N. So the x and y components have to be 0N as well. Finding the tension in the y direction is easy because it is equal (in magnitude) to the gravitational force on the sphere. The x is proving a bit more challenging. I know that the tension in the x is going to be equal (in magnitude) to the electric force due to repulsion. My problem is that I don't know what the separation of the charges is, and can't figure a way to cancel it out of the problem.
I would really appreciate some advice, rather than someone just solving it for me.
Thanks a lot!

 

[Gokul43201]

Assume that both balls are suspended from the same point. So if the semivertical angle is $\theta$, the separation will be $sin \theta$.