fact: Definition PI_2_aux : {z | 7/8 <= z <= 7/4 /\ -cos z = 0}.
imports: Rbase Rfunctions SeqSeries Rtrigo_fun Rtrigo_def Rtrigo_alt Cos_rel Cos_plus ZArith_base Zcomplements Lia Lra Ranalysis1 Rsqrt_def PSeries_reg