Finite Number of Charges around a regular Polygon I know this is probably an easy one, but I'm just unsure... There are 13 equal charges, q, that are placed at the corners of a regular 13-sided polygon. a) What is the Force on a test charge Q at the centre? What I've been donig is simply saying that all but three of the charges will cancel with the remaining three charges having a Y shape. then here, the total force F =2Fcos(theta) -F and then calculated theta as 2pi/13 (F is the force of one point charge). Is this right? it seems very complicated for what at first glance seems like a simple question. b) If one of the 13 charges is removed, what is the force on Q? In this case I have: F=Fcos[theta] - F. Again, this just doesn't "feel" right. Can anyone help?