| Step | Hyp | Ref | Expression | 
						
							| 1 |  | 0ex |  |-  (/) e. _V | 
						
							| 2 |  | base0 |  |-  (/) = ( Base ` (/) ) | 
						
							| 3 |  | 00lss |  |-  (/) = ( LSubSp ` (/) ) | 
						
							| 4 |  | eqid |  |-  ( LSpan ` (/) ) = ( LSpan ` (/) ) | 
						
							| 5 | 2 3 4 | lspfval |  |-  ( (/) e. _V -> ( LSpan ` (/) ) = ( a e. ~P (/) |-> |^| { b e. (/) | a C_ b } ) ) | 
						
							| 6 | 1 5 | ax-mp |  |-  ( LSpan ` (/) ) = ( a e. ~P (/) |-> |^| { b e. (/) | a C_ b } ) | 
						
							| 7 |  | eqid |  |-  ( a e. ~P (/) |-> |^| { b e. (/) | a C_ b } ) = ( a e. ~P (/) |-> |^| { b e. (/) | a C_ b } ) | 
						
							| 8 | 7 | dmmpt |  |-  dom ( a e. ~P (/) |-> |^| { b e. (/) | a C_ b } ) = { a e. ~P (/) | |^| { b e. (/) | a C_ b } e. _V } | 
						
							| 9 |  | rab0 |  |-  { b e. (/) | a C_ b } = (/) | 
						
							| 10 | 9 | inteqi |  |-  |^| { b e. (/) | a C_ b } = |^| (/) | 
						
							| 11 |  | int0 |  |-  |^| (/) = _V | 
						
							| 12 | 10 11 | eqtri |  |-  |^| { b e. (/) | a C_ b } = _V | 
						
							| 13 |  | vprc |  |-  -. _V e. _V | 
						
							| 14 | 12 13 | eqneltri |  |-  -. |^| { b e. (/) | a C_ b } e. _V | 
						
							| 15 | 14 | rgenw |  |-  A. a e. ~P (/) -. |^| { b e. (/) | a C_ b } e. _V | 
						
							| 16 |  | rabeq0 |  |-  ( { a e. ~P (/) | |^| { b e. (/) | a C_ b } e. _V } = (/) <-> A. a e. ~P (/) -. |^| { b e. (/) | a C_ b } e. _V ) | 
						
							| 17 | 15 16 | mpbir |  |-  { a e. ~P (/) | |^| { b e. (/) | a C_ b } e. _V } = (/) | 
						
							| 18 | 8 17 | eqtri |  |-  dom ( a e. ~P (/) |-> |^| { b e. (/) | a C_ b } ) = (/) | 
						
							| 19 |  | mptrel |  |-  Rel ( a e. ~P (/) |-> |^| { b e. (/) | a C_ b } ) | 
						
							| 20 |  | reldm0 |  |-  ( Rel ( a e. ~P (/) |-> |^| { b e. (/) | a C_ b } ) -> ( ( a e. ~P (/) |-> |^| { b e. (/) | a C_ b } ) = (/) <-> dom ( a e. ~P (/) |-> |^| { b e. (/) | a C_ b } ) = (/) ) ) | 
						
							| 21 | 19 20 | ax-mp |  |-  ( ( a e. ~P (/) |-> |^| { b e. (/) | a C_ b } ) = (/) <-> dom ( a e. ~P (/) |-> |^| { b e. (/) | a C_ b } ) = (/) ) | 
						
							| 22 | 18 21 | mpbir |  |-  ( a e. ~P (/) |-> |^| { b e. (/) | a C_ b } ) = (/) | 
						
							| 23 | 6 22 | eqtr2i |  |-  (/) = ( LSpan ` (/) ) |