Charges placed in right triangle pls HELP

[sunny.heyar]

Homework Statement

Charges q1, q2, q3 are placed in a right triangle.
Charges are given, distance between charges is given.
Find the electrical field strength at point "A" which is in the middle of the hypotenuse.
Which equations and how would I figure that out knowing that I have to give magnitude and direction?

Homework Equations

E=kq/r^2 --> ?not sure

The Attempt at a Solution

I drew out a diagram and found all the angle, after that I am completely lost.

 

[rl.bhat]

In a right angled triangle, mid point of the hypotenuse is equidistant from three vertexes.
At A, two fields are in the opposite direction due to two charges at the ends of the hypotenuse. Find the resultant of these two. You can find the angle between the resultant of the two field and third field,and resultant of all the three fields.