Making #z = x-y# we have #(dz)/(dx)=1-(dy)/(dx)# so
#(dy)/(dx)=sin(x-y)-> (dz)/(dx)=1-sin(z)# This differential equation is separable so
#(dz)/(1-sin(z))=dx# integrating
#(2sin(z/2))/(cos(z/2)-sin(z/2))=x + C# or
#2/(cot(z/2)-1)=x+C# or
#2/(cot((x-y)/2)-1)=x+C#
Finally
#y = x-2("arccot"((x+2+C)/(x+C))+k pi)#