Step |
Hyp |
Ref |
Expression |
1 |
|
uvtxnm1nbgr.v |
|- V = ( Vtx ` G ) |
2 |
1
|
uvtxnbgr |
|- ( N e. ( UnivVtx ` G ) -> ( G NeighbVtx N ) = ( V \ { N } ) ) |
3 |
2
|
adantl |
|- ( ( G e. FinUSGraph /\ N e. ( UnivVtx ` G ) ) -> ( G NeighbVtx N ) = ( V \ { N } ) ) |
4 |
3
|
fveq2d |
|- ( ( G e. FinUSGraph /\ N e. ( UnivVtx ` G ) ) -> ( # ` ( G NeighbVtx N ) ) = ( # ` ( V \ { N } ) ) ) |
5 |
1
|
fusgrvtxfi |
|- ( G e. FinUSGraph -> V e. Fin ) |
6 |
1
|
uvtxisvtx |
|- ( N e. ( UnivVtx ` G ) -> N e. V ) |
7 |
6
|
snssd |
|- ( N e. ( UnivVtx ` G ) -> { N } C_ V ) |
8 |
|
hashssdif |
|- ( ( V e. Fin /\ { N } C_ V ) -> ( # ` ( V \ { N } ) ) = ( ( # ` V ) - ( # ` { N } ) ) ) |
9 |
5 7 8
|
syl2an |
|- ( ( G e. FinUSGraph /\ N e. ( UnivVtx ` G ) ) -> ( # ` ( V \ { N } ) ) = ( ( # ` V ) - ( # ` { N } ) ) ) |
10 |
|
hashsng |
|- ( N e. ( UnivVtx ` G ) -> ( # ` { N } ) = 1 ) |
11 |
10
|
adantl |
|- ( ( G e. FinUSGraph /\ N e. ( UnivVtx ` G ) ) -> ( # ` { N } ) = 1 ) |
12 |
11
|
oveq2d |
|- ( ( G e. FinUSGraph /\ N e. ( UnivVtx ` G ) ) -> ( ( # ` V ) - ( # ` { N } ) ) = ( ( # ` V ) - 1 ) ) |
13 |
4 9 12
|
3eqtrd |
|- ( ( G e. FinUSGraph /\ N e. ( UnivVtx ` G ) ) -> ( # ` ( G NeighbVtx N ) ) = ( ( # ` V ) - 1 ) ) |