Definition change_x0y0 :=
  change_x0 E (F -> G) eq_E_dec t x0 (change_x0 F G eq_F_dec (t x0) y0 z0).

Lemma elsewhere2 : forall (x : E) (y : F), x <> x0 \/ y <> y0 -> change_x0y0 x y = t x y.