Electric Field caused by two charges problem

[pstir2]

Homework Statement

Two identical point charges, q1 = +2.5 x 10-6 C and q2 = +2.5 x 10-6 C, are placed as shown in the diagram below. Point P is a distance 0.05 m from q1 and 0.12 m from q2, such that the angle at P is 90 degrees. Calculate the magnitude of the Electric field E at point P.

Homework Equations

Not sure which of these rules would apply. Also I suck at vectors
F = k x q1 x q2 / r^2

E = k x Q / r^2

The Attempt at a Solution

So I have created the diagram and I believe I have to use the second formula twice, along with some trigonometry, but I'm not sure.

 

[haruspex]

I feel you could make a better stab at figuring out which of those equations are likely to be relevant.
Do you know how to determine the field at a point due to a charge at some other point?
Do you know how to add vectors?