When I try and solve for critical points i end up with x=y. Where the domain for the function is inclusivly between and .

If I have infinitely many critical points is there another method to solving this?

Now

So when i set them equal-->

Now I am unsure what to do next, normally i get some critical points, but instead i got infinately many critical points...

EDIT: Here is a link to the graph I think it'll work: http://www.wolframalpha.com/input/?i...sin%28x%2By%29

if not paste this in: graph z=sin(x)+sin(y)+sin(x+y) to get an idea of the graph.

EDIT:Going to bed now, will check again around 12hrs from now...for what it is worth