fact: Definition acos x := if Rle_dec x (-1) then PI else if Rle_dec 1 x then 0 else PI/2 - atan (x/sqrt(1 - x²)).
imports: Lra Rbase PSeries_reg Rtrigo1 Rtrigo_facts Ranalysis_reg Rfunctions AltSeries Rseries SeqProp Ranalysis5 SeqSeries PartSum Lia