Metamath Proof Explorer


Theorem bnj98

Description: Technical lemma for bnj150 . This lemma may no longer be used or have become an indirect lemma of the theorem in question (i.e. a lemma of a lemma... of the theorem). (Contributed by Jonathan Ben-Naim, 3-Jun-2011) (New usage is discouraged.)

Ref Expression
Assertion bnj98
|- A. i e. _om ( suc i e. 1o -> ( F ` suc i ) = U_ y e. ( F ` i ) _pred ( y , A , R ) )

Proof

Step Hyp Ref Expression
1 vex
 |-  i e. _V
2 1 sucid
 |-  i e. suc i
3 2 n0ii
 |-  -. suc i = (/)
4 df-suc
 |-  suc i = ( i u. { i } )
5 df-un
 |-  ( i u. { i } ) = { x | ( x e. i \/ x e. { i } ) }
6 4 5 eqtri
 |-  suc i = { x | ( x e. i \/ x e. { i } ) }
7 df1o2
 |-  1o = { (/) }
8 6 7 eleq12i
 |-  ( suc i e. 1o <-> { x | ( x e. i \/ x e. { i } ) } e. { (/) } )
9 elsni
 |-  ( { x | ( x e. i \/ x e. { i } ) } e. { (/) } -> { x | ( x e. i \/ x e. { i } ) } = (/) )
10 8 9 sylbi
 |-  ( suc i e. 1o -> { x | ( x e. i \/ x e. { i } ) } = (/) )
11 6 10 syl5eq
 |-  ( suc i e. 1o -> suc i = (/) )
12 3 11 mto
 |-  -. suc i e. 1o
13 12 pm2.21i
 |-  ( suc i e. 1o -> ( F ` suc i ) = U_ y e. ( F ` i ) _pred ( y , A , R ) )
14 13 rgenw
 |-  A. i e. _om ( suc i e. 1o -> ( F ` suc i ) = U_ y e. ( F ` i ) _pred ( y , A , R ) )