Force on particle: Coulomb

Roodles01

1. The problem statement, all variables and given/known data
I have a simple question about forces on separated particles, but still need a bit of help. I have put down what I can:

3 particles;
A on y-axis @ √3, charge "q"
B & C each on x-axis, symmetrical about origin, separated by 2a, both charge "q".

Find magnitude & direction of force acting on A due to B & C.


2. Relevant equations
Coulombs law FAB[/SUB] = (q1 q2)/4∏ε₀r_AB r_AB hat
All force should be attractive so
Resultant force on A should be 2x force from either A or B? Yes?
So should now become
FAB = (2 q²)/4∏ε₀r_AB r_AB hat

r, from trig ratios, should be . . . . er . . . . √(a²+3) . . . . . feeling foolish here please help


Then F[/SUB] AB[SUB] = 2q² / ∏ε₀√(a^2+3)