proposition: Lemma pi_ge2 : 2 <= pi.
proof: Proof. by have := pihalf_ge1; rewrite ler_pdivlMr// mul1r. 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