#sin^2x/y^2-sin^2y/x^2=16# and multiplying both sides by #x^2y^2#
#hArrx^2sin^2x-y^2sin^2y=16x^2y^2#
Now differentiating both sides, with respect to #x#, note whenever we have a function of #y#, we differentiate w.r.t. #y# and multiply by #(dy)/(dx)#
#2x xxsin^2x+x^2xx2sinx xxcosx-2ysin^2yxx(dy)/(dx)-y^2xx2siny xxcosyxx(dy)/(dx)=16xx2x xxy^2+16x^2xx2yxx(dy)/(dx)# or
#2xsin^2x+4x^2sinxcosx-2ysin^2y(dy)/(dx)-2y^2siny cosy(dy)/(dx)=32xy^2+32x^2y(dy)/(dx)# or
#32x^2y(dy)/(dx)+2ysin^2y(dy)/(dx)+2y^2siny cosy(dy)/(dx)=2xsin^2x+4x^2sinxcosx-32xy^2# or
#(dy)/(dx)=(2xsin^2x+4x^2sinxcosx-32xy^2)/(32x^2y+2ysin^2y+2y^2siny cosy)#
= #(xsin^2x+2x^2sinxcosx-16xy^2)/(16x^2y+ysin^2y+y^2siny cosy)#