Here is the question statement:
Construct a Gaussian surface S that consists of a cube of side 2, centered at the origin.
Calculate \oint E\bullet d\vec{a} for the point charge, using this surface, thus verifying (or not?) Gauss’ Law.
So I don't think that the symmetry argument will be...
What would the cosθ be in terms of x,y and/or z? I am trying to do a proof of this that shows the result of Q/ε for the whole cube. On my first run through I did not account for the spherical distribution of the e-field and I was on the way to get a value of 0. I figured cosθ need to be included...