1. The problem statement, all variables and given/known data [itex]u = x^u + u^y[/itex] Find the partial derivatives of ##u## w.r.t. ##x, y##. 2. Relevant equations Only the one. 3. The attempt at a solution I've attempted reducing the problem using logs, but the resulting equations seem no more tenable to me. I'm sure there is a nice trick... it isn't currently in my tool belt. Edit: A further request if anybody has this information at their fingertips. I've been two years removed from my studies of mathematics and physics... I am planning to return as I've found the 'real world' much less interesting and inspiring. I've been going through some old textbooks as a warmup, and although I can still recall many of the intricate mathematical methods used in various branches of physics, my knowledge of elementary manipulations is pretty darn tattered. Mary Boas' text in mathematical methods in physics has been a *great* boon; I am curious as to whether or not a similar text exists for one who desires a "handbook" of mathematical theorems, identities, proofs &c. without all of the detailed explanations and problem sets.