proposition: Lemma cosD2pi : periodic cos (pi *+ 2).
proof: Proof. by move=> a; rewrite cosD cos2pi mulr1 sin2pi mulr0 subr0. 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