| Step | Hyp | Ref | Expression | 
						
							| 1 |  | axlowdimlem7.1 |  |-  P = ( { <. 3 , -u 1 >. } u. ( ( ( 1 ... N ) \ { 3 } ) X. { 0 } ) ) | 
						
							| 2 | 1 | fveq1i |  |-  ( P ` K ) = ( ( { <. 3 , -u 1 >. } u. ( ( ( 1 ... N ) \ { 3 } ) X. { 0 } ) ) ` K ) | 
						
							| 3 |  | eldifsn |  |-  ( K e. ( ( 1 ... N ) \ { 3 } ) <-> ( K e. ( 1 ... N ) /\ K =/= 3 ) ) | 
						
							| 4 |  | disjdif |  |-  ( { 3 } i^i ( ( 1 ... N ) \ { 3 } ) ) = (/) | 
						
							| 5 |  | 3ex |  |-  3 e. _V | 
						
							| 6 |  | negex |  |-  -u 1 e. _V | 
						
							| 7 | 5 6 | fnsn |  |-  { <. 3 , -u 1 >. } Fn { 3 } | 
						
							| 8 |  | c0ex |  |-  0 e. _V | 
						
							| 9 | 8 | fconst |  |-  ( ( ( 1 ... N ) \ { 3 } ) X. { 0 } ) : ( ( 1 ... N ) \ { 3 } ) --> { 0 } | 
						
							| 10 |  | ffn |  |-  ( ( ( ( 1 ... N ) \ { 3 } ) X. { 0 } ) : ( ( 1 ... N ) \ { 3 } ) --> { 0 } -> ( ( ( 1 ... N ) \ { 3 } ) X. { 0 } ) Fn ( ( 1 ... N ) \ { 3 } ) ) | 
						
							| 11 | 9 10 | ax-mp |  |-  ( ( ( 1 ... N ) \ { 3 } ) X. { 0 } ) Fn ( ( 1 ... N ) \ { 3 } ) | 
						
							| 12 |  | fvun2 |  |-  ( ( { <. 3 , -u 1 >. } Fn { 3 } /\ ( ( ( 1 ... N ) \ { 3 } ) X. { 0 } ) Fn ( ( 1 ... N ) \ { 3 } ) /\ ( ( { 3 } i^i ( ( 1 ... N ) \ { 3 } ) ) = (/) /\ K e. ( ( 1 ... N ) \ { 3 } ) ) ) -> ( ( { <. 3 , -u 1 >. } u. ( ( ( 1 ... N ) \ { 3 } ) X. { 0 } ) ) ` K ) = ( ( ( ( 1 ... N ) \ { 3 } ) X. { 0 } ) ` K ) ) | 
						
							| 13 | 7 11 12 | mp3an12 |  |-  ( ( ( { 3 } i^i ( ( 1 ... N ) \ { 3 } ) ) = (/) /\ K e. ( ( 1 ... N ) \ { 3 } ) ) -> ( ( { <. 3 , -u 1 >. } u. ( ( ( 1 ... N ) \ { 3 } ) X. { 0 } ) ) ` K ) = ( ( ( ( 1 ... N ) \ { 3 } ) X. { 0 } ) ` K ) ) | 
						
							| 14 | 4 13 | mpan |  |-  ( K e. ( ( 1 ... N ) \ { 3 } ) -> ( ( { <. 3 , -u 1 >. } u. ( ( ( 1 ... N ) \ { 3 } ) X. { 0 } ) ) ` K ) = ( ( ( ( 1 ... N ) \ { 3 } ) X. { 0 } ) ` K ) ) | 
						
							| 15 | 8 | fvconst2 |  |-  ( K e. ( ( 1 ... N ) \ { 3 } ) -> ( ( ( ( 1 ... N ) \ { 3 } ) X. { 0 } ) ` K ) = 0 ) | 
						
							| 16 | 14 15 | eqtrd |  |-  ( K e. ( ( 1 ... N ) \ { 3 } ) -> ( ( { <. 3 , -u 1 >. } u. ( ( ( 1 ... N ) \ { 3 } ) X. { 0 } ) ) ` K ) = 0 ) | 
						
							| 17 | 3 16 | sylbir |  |-  ( ( K e. ( 1 ... N ) /\ K =/= 3 ) -> ( ( { <. 3 , -u 1 >. } u. ( ( ( 1 ... N ) \ { 3 } ) X. { 0 } ) ) ` K ) = 0 ) | 
						
							| 18 | 2 17 | eqtrid |  |-  ( ( K e. ( 1 ... N ) /\ K =/= 3 ) -> ( P ` K ) = 0 ) |