I'm running through the following problem in an EM text of mine: Calculate the flux of a point charge Q at the origin through a cube centered through the origin by both direct integration and Gauss's Law (essentially prove Gauss's Law for a point charge). Now I got the answer of Q/ε0 via direct integration alright. When I go to use Gauss's Law in Cartesian coordiantes I keep getting zero, however if I "surround" the cube with an imaginary spherical surface and take the flux through that in Spherical I get the correct answer. I'm trying to reconcile the discrepancy and the only thing I can come up with is that I might have to incorporate the Dirac-Delta Function to account for the fact that I'm dealing with a point charge to do this in Cartesian. Is this accurate to assume? I have that E(r)=(Q/4πε0)(r-3)(r) Where r=xi+yj+zk Every time I take the divergence of E in Cartesian and simplify, I end up getting zero. I basically tried generalizing doing the partial derivative instead of doing a derivative for each coordinate. Let s be the coordinate that I'm differentiating with respect to (i.e. I'm looking at ∂Es/∂s) in figuring out the divergence (i.e. ∂Ex/∂x+∂Ey/∂y+∂Ez/∂z). I am taking the Es to be (Q/4πε0)*s*(s2+r2+t2)-3/2where r and t are the other coordinates which are not being taken a derivative for. For ∂Es I keep getting (Q/4πε0)*(s2+r2+t2)-5/2*(r2+t2-2s2). When I apply this to each coordinate choice (s=x,s=y,s=z) and try to take the sum to get the divergence, I keep getting zero.