proposition: Lemma cosDpi : alternating cos pi.
proof: Proof. by move=> a; rewrite cosD cospi mulrN1 sinpi 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