proposition: Lemma derivable_pt_in_mult: forall (D : R -> Prop) f g x, D x -> derivable_pt_in D f x -> derivable_pt_in D g x -> derivable_pt_in D (f * g)%F x.
proof: Proof. intros D f g x x_in [] [] ; eexists ; eapply derivable_pt_lim_in_mult ; eassumption. Qed.
imports: Rbase Ranalysis Rinterval Rfunctions Rfunction_def Rfunction_facts Ranalysis_def Ranalysis_def_simpl Ranalysis_continuity MyRIneq MyR_dist Lra Tactics