proposition: Lemma sinB x y : sin (x - y) = sin x * cos y - cos x * sin y.
proof: Proof. by rewrite sinD cosN sinN mulrN. 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