*m*and identical charge

*q*hang from nonconducting threads of length

*L*. Assume that

*θ*is so small that tan(

*θ*) can be replaced by its approximate equal, sin(

*θ*).

(a) Show that equilibrium separation

*x*of the balls is given by the equation below.

I know to use Coulomb's Law [ q1*q2/(4*pi*epsilon*r^2) ] but I'm unable to prove the given equation from that. I can't get passed the effects of changing theta as q and/or m change. Can someone give me a step-by-step explanation on this? Thank you.