End Well_founded.
(** Well-founded fixpoints over pairs *)
Section Well_founded_2.
Variables A B : Type.
Variable R : A * B -> A * B -> Prop.
Variable P : A -> B -> Type.
Section FixPoint_2.
Variable
F :
forall (x:A) (x':B),
(forall (y:A) (y':B), R (y, y') (x, x') -> P y y') -> P x x'.
Fixpoint Fix_F_2 (x:A) (x':B) (a:Acc R (x, x')) : P x x' :=
F
(fun (y:A) (y':B) (h:R (y, y') (x, x')) =>
Fix_F_2 (x:=y) (x':=y') (Acc_inv a (y,y') h)).
End FixPoint_2.
Hypothesis Rwf : well_founded R.

Theorem well_founded_induction_type_2 :
(forall (x:A) (x':B),
(forall (y:A) (y':B), R (y, y') (x, x') -> P y y') -> P x x') ->
forall (a:A) (b:B), P a b.