Electric Field at Midpoint of Equilateral Triangle

[Brit412]

Homework Statement

The figure shows a system consisting of three charges, q1=+5.0uC, q2=+5.0uC and
q3=-5.0uC, at the vertices of an equilateral triangle (with q2 at the top point of the triangle).
Find the magnitude of the electric field at a point halfway between the charges q1 and q2.
distance= 2.95cm

Homework Equations

i know an equation is E= k q/r^2

The Attempt at a Solution

So since it wanted to know the halfway point, I divided the distance between the points in half and used it as r. And I figured that the charges have an x and y component but what angles do I use??

 

[rl.bhat]

Triangle is equilateral. So the sides are equal. Find the distance between the charge q3 and the mid point of charge q1 and q2. The line joining q3 and mid point is perpendicular to the line joining q1 and q2.

 

[Brit412]

I got a pretty big number (a number times 10^8). That seems too big??