These have been driving me crazy. The book is terrible at explaining this stuff, so I was hoping someone here could help me out. 1. The problem statement, all variables and given/known data A rectangle has a length of 2d and a height of d. Each of the following three charges is located at a corner of the rectangle: +q1 (upper left corner), +q2 (lower right corner), and -q (lower left corner). The net electric field at the (empty) upper right corner is zero. Find the magnitudes of q1 and q2. Express your answers in terms of q. 2. Relevant equations Coloumb's Law: k * (|q1| * |q2| / r2) Where k= a proportionality constant ~ 8.99 * 109 N * m2/C2 Electric Field Definition: E = F / q0 Where E is the net electric field at a point, and F is the force experienced by a small test charge represented by q0 3. The attempt at a solution I really got nowhere trying to find this solution, but here's what I tried: --> I defined the upper right corner where the net electric field is zero as point T (for easy reference). --> I represented the forces exerted on point T as three vectors, all with unknown magnitudes. The vector created by q1 had a direction of 0º; the vector created by q2 had a direction of arctan(2)~63.43º (reasoning below), and the vector created by -q had a direction of 270º. --> I obtained the direction of the vector created by q2 by drawing a right triangle with leg lengths 1 and 2 and solving for the angle opposite the side with length 2. The leg lengths were obtained from the given data that the sides of the rectangle are d and 2d. --> At this point, I realized I was completely on the wrong track. I was planning on solving for the resultant of these three vectors, but I realized that it was already given in the problem that the resultant is, in effect, zero. Thus, in my line of thought, the resultant of the vectors produced by q1 and q2 (the positive charges) must be equal in magnitude and opposite in direction of the vector produced by -q. However, because the two vectors produced by these positive charges are at 0º and ~63.43º, they cannot produce a resultant at 90º, which would be needed in order to have the opposite direction of the vector created by then negative charge. Thus, to me, the problem appears impossible, unless q1 or q2 were allowed to be negative, which I don't believe they are. Thanks a ton for any help you can provide!