Metamath Proof Explorer


Theorem tfr2ALT

Description: Alternate proof of tfr2 using well-ordered recursion. (Contributed by Scott Fenton, 3-Aug-2020) (New usage is discouraged.) (Proof modification is discouraged.)

Ref Expression
Hypothesis tfrALT.1
|- F = recs ( G )
Assertion tfr2ALT
|- ( A e. On -> ( F ` A ) = ( G ` ( F |` A ) ) )

Proof

Step Hyp Ref Expression
1 tfrALT.1
 |-  F = recs ( G )
2 epweon
 |-  _E We On
3 epse
 |-  _E Se On
4 df-recs
 |-  recs ( G ) = wrecs ( _E , On , G )
5 1 4 eqtri
 |-  F = wrecs ( _E , On , G )
6 2 3 5 wfr2
 |-  ( A e. On -> ( F ` A ) = ( G ` ( F |` Pred ( _E , On , A ) ) ) )
7 predon
 |-  ( A e. On -> Pred ( _E , On , A ) = A )
8 7 reseq2d
 |-  ( A e. On -> ( F |` Pred ( _E , On , A ) ) = ( F |` A ) )
9 8 fveq2d
 |-  ( A e. On -> ( G ` ( F |` Pred ( _E , On , A ) ) ) = ( G ` ( F |` A ) ) )
10 6 9 eqtrd
 |-  ( A e. On -> ( F ` A ) = ( G ` ( F |` A ) ) )