Metamath Proof Explorer


Theorem scottelrankd

Description: Property of a Scott's trick set. (Contributed by Rohan Ridenour, 11-Aug-2023)

Ref Expression
Hypotheses scottelrankd.1
|- ( ph -> B e. Scott A )
scottelrankd.2
|- ( ph -> C e. Scott A )
Assertion scottelrankd
|- ( ph -> ( rank ` B ) C_ ( rank ` C ) )

Proof

Step Hyp Ref Expression
1 scottelrankd.1
 |-  ( ph -> B e. Scott A )
2 scottelrankd.2
 |-  ( ph -> C e. Scott A )
3 fveq2
 |-  ( y = C -> ( rank ` y ) = ( rank ` C ) )
4 3 sseq2d
 |-  ( y = C -> ( ( rank ` B ) C_ ( rank ` y ) <-> ( rank ` B ) C_ ( rank ` C ) ) )
5 df-scott
 |-  Scott A = { x e. A | A. y e. A ( rank ` x ) C_ ( rank ` y ) }
6 1 5 eleqtrdi
 |-  ( ph -> B e. { x e. A | A. y e. A ( rank ` x ) C_ ( rank ` y ) } )
7 fveq2
 |-  ( x = B -> ( rank ` x ) = ( rank ` B ) )
8 7 sseq1d
 |-  ( x = B -> ( ( rank ` x ) C_ ( rank ` y ) <-> ( rank ` B ) C_ ( rank ` y ) ) )
9 8 ralbidv
 |-  ( x = B -> ( A. y e. A ( rank ` x ) C_ ( rank ` y ) <-> A. y e. A ( rank ` B ) C_ ( rank ` y ) ) )
10 9 elrab
 |-  ( B e. { x e. A | A. y e. A ( rank ` x ) C_ ( rank ` y ) } <-> ( B e. A /\ A. y e. A ( rank ` B ) C_ ( rank ` y ) ) )
11 6 10 sylib
 |-  ( ph -> ( B e. A /\ A. y e. A ( rank ` B ) C_ ( rank ` y ) ) )
12 11 simprd
 |-  ( ph -> A. y e. A ( rank ` B ) C_ ( rank ` y ) )
13 2 5 eleqtrdi
 |-  ( ph -> C e. { x e. A | A. y e. A ( rank ` x ) C_ ( rank ` y ) } )
14 elrabi
 |-  ( C e. { x e. A | A. y e. A ( rank ` x ) C_ ( rank ` y ) } -> C e. A )
15 13 14 syl
 |-  ( ph -> C e. A )
16 4 12 15 rspcdva
 |-  ( ph -> ( rank ` B ) C_ ( rank ` C ) )