Instance paco2_inst  T0 T1 (gf : rel2 T0 T1->_) r x0 x1 : paco_class (paco2 gf r x0 x1) :=
{ pacoacc    := paco2_acc gf;
  pacomult   := paco2_mult gf;
  pacofold   := paco2_fold gf;
  pacounfold := paco2_unfold gf }.Definition monotone2_2 T0 T1 (gf: rel2 T0 T1 -> rel2 T0 T1 -> rel2 T0 T1) :=
  forall x0 x1 r_0 r_1 r'_0 r'_1 (IN: gf r_0 r_1 x0 x1) (LE_0: r_0 <2= r'_0)(LE_1: r_1 <2= r'_1), gf r'_0 r'_1 x0 x1.

Theorem paco2_2_1_acc: forall l r_0 r_1 (OBG: forall rr (INC: r_1 <2= rr) (CIH: l <_paco_2= rr), l <_paco_2= paco2_2_1 gf_0 gf_1 r_0 rr), l <2= paco2_2_1 gf_0 gf_1 r_0 r_1.