Particles 2 and 4, of charge -e, are fixed in place on the y axis at y_{2}=-10.00 cm and y_{4}=5.00cm. Particles 1 and 3, of charge -e, can be moved along the x axis. Particle 5 of charge +e is fixed at the origin. Initially particle 1 is at x_{1}= -10.0cm and particle 3 is at x_{3}= 10.0cm. (a) to what x value must particle 1 be moved to rotate the direction of the net electric force F_{net} on particle 5 by  30 degrees counterclockwise? (b) With particle 1 fixed at the new position, to what x value must you move particle 3 to rotate F_{net} back to its original position?

I used Coulomb's Law to derive the individual forces and the net force but I am having problems working in the rotation. I know what the right answer is but can't seem to get there.