When I use d, I am referring to a partial derivative here. So where w(z)=u(x,y) + iv(x,y), and the derivative of w(z) exists, I have shown that (du/dx)(du/dy) + (dv/dx)(dv/dy) = 0 But I have to give a geometric interpretation of this which is somewhat confusing to me. I am not sure what do here. Should I start by constructing vectors normal to the curve u(x,y)=c1 and v(x,y)=c2? And if so, how do I do this? Thanks for reading and wasting your time on me.