It is clear from the diagram on the left that F 1 y = F 1 sin 45° and F 2 y = F 2 sin 45°.
Also, the magnitude of F 1 equals that of F 2. So the net electric force on the negative
charge is F 1 y + F 2 y = 2F sin 45°, where F is the strength of the force between the
negative charge and each of the positive charges.
The direction of the net force is straight upward, toward the center of the line that
joins the two positive charges.