proposition: Lemma sinDpihalf a : sin (a + pi / 2) = cos a.
proof: Proof. by rewrite sinD cos_pihalf mulr0 add0r sin_pihalf mulr1. 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