proposition: Lemma acos1 : acos (1 : R) = 0.
proof: Proof. by have := @cosK 0; rewrite cos0 => -> //; rewrite in_itv //= lexx pi_ge0. 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