DYDZZY:=proc(f)
# DYDZZY(f) is used to get the derivate of
# 	    an implicit function
local Eq,deq,imderiv;
Eq:='Eq';
Eq:=f;
deq:=diff(Eq,x);
readlib(isolate);
imderiv:=isolate(deq,diff(y(x),x));
end;