www.pudn.com > matlab8.zip > DYDZZY.src

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;