fact: Definition inv_r_helper (xi zi : FF) := Flt2_m1 (lower xi) && Fpos0 (Fplus2 (Fplus2 (lower xi) (upper zi)) (Fmult2 (lower xi) (upper zi))) && Fneg0 (Fplus2 (Fplus2 (upper xi) (lower zi)) (Fmult2 (upper xi) (lower zi))).
imports: Gappa_common Gappa_pred_bnd