How Is the Net Gravitational Force Calculated in a Triangular Particle System?

[Demonsthenes]

Homework Statement

Three identical spherical particles of mass m are each located at the corners of an equilateral triangle with edge length r (each sphere is centered at each corner). Show the magnitude of the net gravitational force on anyone of the particles due to the other two particles is given by:

Homework Equations

Fg = sqrt(3) Gm^2/r^2

The Attempt at a Solution

Again... had no idea where to start.

 

[huyen_vyvy]

what's the gravitational force between each pair? and then sum the 2 vectors (i.e, 2 forces acting on 1 particle) using geometry to find the magnetude of the force.