1. The problem statement, all variables and given/known data there is a square on the XoY plane, centered at the origin (just outlines of the square) it has a charge Q (Q>0) and side 2L, i must evaluate the electric field along the z axis. see attached image 2. Relevant equations E=k*q/r^2 3. The attempt at a solution So first i divided the square into 4 lines, and noticed that due to the simmetry there is only a field in the z direction, and all the lines of the square contribute the same to that field. So: dE= k(Q/8L)1* dx/(x2+y2+z2)2*(z/(x2+y2+z2))½)3 where subscrip1 is Q/8L because the full Q is for the whole square, so we divide it by 4 to get the charge on the line and divide again by 2L to get the charge density. subscript 2 is the distance of the charge to the line. subscript 3 is cosine of E with Ez so we get only the z component Now the integral, i get an not-so-straightforward integral, so if there is a simplification i could do here please advise. so i get E= k(Q/8L)z*∫dx/((x2+y2+z2)3/2)) and i integrate either over -L to L or from 0 to L and multiply it by 2. and i get E=kQz*1/((y2+z2)*(L2+y2+z2)½) This result makes sense to me physically, as field is 0 when z is 0 (makes sense since field would no longer have a z component) and also goes to 0 when z goes to infinity. So the total field is 4*E. Am i correct? any simplification suggestions for the integral EDIT: oh and y should be L since its fixed.