proposition: Lemma sin0cos1 x : sin x = 0 -> `|cos x| = 1.
proof: Proof. by move/eqP; rewrite -norm_cos_eq1 => /eqP. Qed.
imports: mathcomp(all_ssreflect ssralg ssrint ssrnum matrix) mathcomp(interval rat) mathcomp(mathcomp_extra boolp classical_sets functions) reals ereal nsatz_realtype signed topology normedtype landau sequences derive realfun exp