1. The problem statement, all variables and given/known data Find the electric field of a charge at a corner if there are 4 equal charges at the corner of a rectangle with sides 40 cm and 20 cm. The charges are 2.5 x 10^3 C. 2. Relevant equations E = (kq)/r^2 3. The attempt at a solution I labelled the top left charge q1, the top right charge q2, the bottom left charge q3, and the bottom right charge q4. The corner I picked to find the electric field was the top right corner, at q2. So what I'm going to do is find all the charges acting horizontally and vertically, then I apply pythagorean's theorem to find the net charge. Is that right so far? So I took the charge of q1 acting on the top right corner, the charge of q4 acting upwards on the top right corner, and the charge of q3 on the top right corner. I'll put in some numbers after I know I'm on the right track.