1. Problem statement In a two-dimensional problem, σx=300xy and σy=300xy and τxy=0 at x=y=0. Determine lines of constant shear stress τxy in the x-y plane and plot them for τxy=100, 300, 400. 2. Relevant equations dσx/dx + dτxy/dy + X = 0  dτxy/dx + dσy/dy + Y = 0  At least I think these are the ones I need. 3. The attempt at a solution First off, when τxy is constant both dτxy/dx and dτxy/dy should be 0. Further more, to simplify the problem I assume that the body forces X and Y are 0. Then : dσx/dx = 300y and dσy/dy = 300x which can then be filled into equation  and  and I can then calculate for which values of x and y both terms end up as 0. However if I do this, I (offcourse) end up with the equation y=x which seems a little simple to me and from this result I have no idea to plot lineS for the values of τxy as given in the assignment. So actually, I think I'm either approaching this problem with a completely wrong method or I'm missing a part of the problem. Any help or hints will be very much appreciated!