Answer to Question #76442 in Calculus for BIVEK SAH

Question

If f(x,y)=x^2tan^-1(y/x)y^2tan^-1(x/y)[xnot=0,y not=0]
=0(x=0=y)
then show that
(Partial d^2f)/(partial dx *partial day)=(x^2-y^2)/(x^2+y^2)