proposition: Lemma sin_mulr2n x : sin (x *+ 2) = (cos x * sin x) *+ 2.
proof: Proof. by rewrite mulr2n sinD mulrC -mulr2n. 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