*To*: mathgroup@smc.vnet.net*Subject*: [mg10844] How do u go about doing this---?*From*: "McAllister" <lmcallister@email.msn.com>*Date*: Tue, 10 Feb 1998 21:01:55 -0500

Let f(x) = sin(x)+cos(y) ----------------- sin(x) - cos(y) Show that (df/dx)^2 + (df/dy)^2 = 2+cos(2(x-y))+cos(2(x+y)) ----------------------------------- (sin(x)-cos(y))^4 Thanks, L.