1. The problem statement, all variables and given/known data (Q) Compute the surface integral g = xy over the triangle x+y+z=1, x,y,z>=0. 2. Relevant equations 3. The attempt at a solution The triangular region basically means that the region in consideration is a plane and not a sphere, cylinder etc..... Therefore, we can let the region r be defined as r = xi + yj + (1-x-y)k. thus, partial derivative of r w.r.t x = i-k and that w.r.t y = j-k. their cross product comes to -i+j+k. the modulus of this is of course sqrt(3). So the double integral will be the double integral over region R of sqrt(3)xydA. the problem is, I have no idea as to how I can find the limits of this double integral. Please advice. Thank-you very much for your time and effort!!!!!