d/dx(u^v) =
(uv^v-1)dv/dx +(uv^v) du/dx
(vu^v-1)du/dx +((Inu)u^v) dv/dx
(uv^u-1)du/dv +((Inu)v^u) dx/dx
(v^u-1)du/dv +((Inu)^u) dy/dx