proposition: Lemma derive_pt_mirr : forall f (x:R) (pr1:derivable_pt f (-x)), derive_pt (mirr_fct f) x (derivable_pt_mirr _ _ pr1) = - derive_pt f (-x) pr1.
proof: Proof. intros. apply derive_pt_eq_0. apply derivable_pt_lim_mirr_fwd. rewrite Ropp_involutive. apply (derive_pt_eq_1 _ _ _ pr1). reflexivity. Qed.
imports: Rbase Rfunctions Rlimit Rderiv