| Step | 
						Hyp | 
						Ref | 
						Expression | 
					
						
							| 1 | 
							
								
							 | 
							0sno | 
							 |-  0s e. No  | 
						
						
							| 2 | 
							
								
							 | 
							mulsval | 
							 |-  ( ( A e. No /\ 0s e. No ) -> ( A x.s 0s ) = ( ( { a | E. p e. ( _Left ` A ) E. q e. ( _Left ` 0s ) a = ( ( ( p x.s 0s ) +s ( A x.s q ) ) -s ( p x.s q ) ) } u. { b | E. r e. ( _Right ` A ) E. s e. ( _Right ` 0s ) b = ( ( ( r x.s 0s ) +s ( A x.s s ) ) -s ( r x.s s ) ) } ) |s ( { c | E. t e. ( _Left ` A ) E. u e. ( _Right ` 0s ) c = ( ( ( t x.s 0s ) +s ( A x.s u ) ) -s ( t x.s u ) ) } u. { d | E. v e. ( _Right ` A ) E. w e. ( _Left ` 0s ) d = ( ( ( v x.s 0s ) +s ( A x.s w ) ) -s ( v x.s w ) ) } ) ) ) | 
						
						
							| 3 | 
							
								1 2
							 | 
							mpan2 | 
							 |-  ( A e. No -> ( A x.s 0s ) = ( ( { a | E. p e. ( _Left ` A ) E. q e. ( _Left ` 0s ) a = ( ( ( p x.s 0s ) +s ( A x.s q ) ) -s ( p x.s q ) ) } u. { b | E. r e. ( _Right ` A ) E. s e. ( _Right ` 0s ) b = ( ( ( r x.s 0s ) +s ( A x.s s ) ) -s ( r x.s s ) ) } ) |s ( { c | E. t e. ( _Left ` A ) E. u e. ( _Right ` 0s ) c = ( ( ( t x.s 0s ) +s ( A x.s u ) ) -s ( t x.s u ) ) } u. { d | E. v e. ( _Right ` A ) E. w e. ( _Left ` 0s ) d = ( ( ( v x.s 0s ) +s ( A x.s w ) ) -s ( v x.s w ) ) } ) ) ) | 
						
						
							| 4 | 
							
								
							 | 
							rex0 | 
							 |-  -. E. q e. (/) a = ( ( ( p x.s 0s ) +s ( A x.s q ) ) -s ( p x.s q ) )  | 
						
						
							| 5 | 
							
								
							 | 
							left0s | 
							 |-  ( _Left ` 0s ) = (/)  | 
						
						
							| 6 | 
							
								5
							 | 
							rexeqi | 
							 |-  ( E. q e. ( _Left ` 0s ) a = ( ( ( p x.s 0s ) +s ( A x.s q ) ) -s ( p x.s q ) ) <-> E. q e. (/) a = ( ( ( p x.s 0s ) +s ( A x.s q ) ) -s ( p x.s q ) ) )  | 
						
						
							| 7 | 
							
								4 6
							 | 
							mtbir | 
							 |-  -. E. q e. ( _Left ` 0s ) a = ( ( ( p x.s 0s ) +s ( A x.s q ) ) -s ( p x.s q ) )  | 
						
						
							| 8 | 
							
								7
							 | 
							a1i | 
							 |-  ( p e. ( _Left ` A ) -> -. E. q e. ( _Left ` 0s ) a = ( ( ( p x.s 0s ) +s ( A x.s q ) ) -s ( p x.s q ) ) )  | 
						
						
							| 9 | 
							
								8
							 | 
							nrex | 
							 |-  -. E. p e. ( _Left ` A ) E. q e. ( _Left ` 0s ) a = ( ( ( p x.s 0s ) +s ( A x.s q ) ) -s ( p x.s q ) )  | 
						
						
							| 10 | 
							
								9
							 | 
							abf | 
							 |-  { a | E. p e. ( _Left ` A ) E. q e. ( _Left ` 0s ) a = ( ( ( p x.s 0s ) +s ( A x.s q ) ) -s ( p x.s q ) ) } = (/) | 
						
						
							| 11 | 
							
								
							 | 
							rex0 | 
							 |-  -. E. s e. (/) b = ( ( ( r x.s 0s ) +s ( A x.s s ) ) -s ( r x.s s ) )  | 
						
						
							| 12 | 
							
								
							 | 
							right0s | 
							 |-  ( _Right ` 0s ) = (/)  | 
						
						
							| 13 | 
							
								12
							 | 
							rexeqi | 
							 |-  ( E. s e. ( _Right ` 0s ) b = ( ( ( r x.s 0s ) +s ( A x.s s ) ) -s ( r x.s s ) ) <-> E. s e. (/) b = ( ( ( r x.s 0s ) +s ( A x.s s ) ) -s ( r x.s s ) ) )  | 
						
						
							| 14 | 
							
								11 13
							 | 
							mtbir | 
							 |-  -. E. s e. ( _Right ` 0s ) b = ( ( ( r x.s 0s ) +s ( A x.s s ) ) -s ( r x.s s ) )  | 
						
						
							| 15 | 
							
								14
							 | 
							a1i | 
							 |-  ( r e. ( _Right ` A ) -> -. E. s e. ( _Right ` 0s ) b = ( ( ( r x.s 0s ) +s ( A x.s s ) ) -s ( r x.s s ) ) )  | 
						
						
							| 16 | 
							
								15
							 | 
							nrex | 
							 |-  -. E. r e. ( _Right ` A ) E. s e. ( _Right ` 0s ) b = ( ( ( r x.s 0s ) +s ( A x.s s ) ) -s ( r x.s s ) )  | 
						
						
							| 17 | 
							
								16
							 | 
							abf | 
							 |-  { b | E. r e. ( _Right ` A ) E. s e. ( _Right ` 0s ) b = ( ( ( r x.s 0s ) +s ( A x.s s ) ) -s ( r x.s s ) ) } = (/) | 
						
						
							| 18 | 
							
								10 17
							 | 
							uneq12i | 
							 |-  ( { a | E. p e. ( _Left ` A ) E. q e. ( _Left ` 0s ) a = ( ( ( p x.s 0s ) +s ( A x.s q ) ) -s ( p x.s q ) ) } u. { b | E. r e. ( _Right ` A ) E. s e. ( _Right ` 0s ) b = ( ( ( r x.s 0s ) +s ( A x.s s ) ) -s ( r x.s s ) ) } ) = ( (/) u. (/) ) | 
						
						
							| 19 | 
							
								
							 | 
							un0 | 
							 |-  ( (/) u. (/) ) = (/)  | 
						
						
							| 20 | 
							
								18 19
							 | 
							eqtri | 
							 |-  ( { a | E. p e. ( _Left ` A ) E. q e. ( _Left ` 0s ) a = ( ( ( p x.s 0s ) +s ( A x.s q ) ) -s ( p x.s q ) ) } u. { b | E. r e. ( _Right ` A ) E. s e. ( _Right ` 0s ) b = ( ( ( r x.s 0s ) +s ( A x.s s ) ) -s ( r x.s s ) ) } ) = (/) | 
						
						
							| 21 | 
							
								
							 | 
							rex0 | 
							 |-  -. E. u e. (/) c = ( ( ( t x.s 0s ) +s ( A x.s u ) ) -s ( t x.s u ) )  | 
						
						
							| 22 | 
							
								12
							 | 
							rexeqi | 
							 |-  ( E. u e. ( _Right ` 0s ) c = ( ( ( t x.s 0s ) +s ( A x.s u ) ) -s ( t x.s u ) ) <-> E. u e. (/) c = ( ( ( t x.s 0s ) +s ( A x.s u ) ) -s ( t x.s u ) ) )  | 
						
						
							| 23 | 
							
								21 22
							 | 
							mtbir | 
							 |-  -. E. u e. ( _Right ` 0s ) c = ( ( ( t x.s 0s ) +s ( A x.s u ) ) -s ( t x.s u ) )  | 
						
						
							| 24 | 
							
								23
							 | 
							a1i | 
							 |-  ( t e. ( _Left ` A ) -> -. E. u e. ( _Right ` 0s ) c = ( ( ( t x.s 0s ) +s ( A x.s u ) ) -s ( t x.s u ) ) )  | 
						
						
							| 25 | 
							
								24
							 | 
							nrex | 
							 |-  -. E. t e. ( _Left ` A ) E. u e. ( _Right ` 0s ) c = ( ( ( t x.s 0s ) +s ( A x.s u ) ) -s ( t x.s u ) )  | 
						
						
							| 26 | 
							
								25
							 | 
							abf | 
							 |-  { c | E. t e. ( _Left ` A ) E. u e. ( _Right ` 0s ) c = ( ( ( t x.s 0s ) +s ( A x.s u ) ) -s ( t x.s u ) ) } = (/) | 
						
						
							| 27 | 
							
								
							 | 
							rex0 | 
							 |-  -. E. w e. (/) d = ( ( ( v x.s 0s ) +s ( A x.s w ) ) -s ( v x.s w ) )  | 
						
						
							| 28 | 
							
								5
							 | 
							rexeqi | 
							 |-  ( E. w e. ( _Left ` 0s ) d = ( ( ( v x.s 0s ) +s ( A x.s w ) ) -s ( v x.s w ) ) <-> E. w e. (/) d = ( ( ( v x.s 0s ) +s ( A x.s w ) ) -s ( v x.s w ) ) )  | 
						
						
							| 29 | 
							
								27 28
							 | 
							mtbir | 
							 |-  -. E. w e. ( _Left ` 0s ) d = ( ( ( v x.s 0s ) +s ( A x.s w ) ) -s ( v x.s w ) )  | 
						
						
							| 30 | 
							
								29
							 | 
							a1i | 
							 |-  ( v e. ( _Right ` A ) -> -. E. w e. ( _Left ` 0s ) d = ( ( ( v x.s 0s ) +s ( A x.s w ) ) -s ( v x.s w ) ) )  | 
						
						
							| 31 | 
							
								30
							 | 
							nrex | 
							 |-  -. E. v e. ( _Right ` A ) E. w e. ( _Left ` 0s ) d = ( ( ( v x.s 0s ) +s ( A x.s w ) ) -s ( v x.s w ) )  | 
						
						
							| 32 | 
							
								31
							 | 
							abf | 
							 |-  { d | E. v e. ( _Right ` A ) E. w e. ( _Left ` 0s ) d = ( ( ( v x.s 0s ) +s ( A x.s w ) ) -s ( v x.s w ) ) } = (/) | 
						
						
							| 33 | 
							
								26 32
							 | 
							uneq12i | 
							 |-  ( { c | E. t e. ( _Left ` A ) E. u e. ( _Right ` 0s ) c = ( ( ( t x.s 0s ) +s ( A x.s u ) ) -s ( t x.s u ) ) } u. { d | E. v e. ( _Right ` A ) E. w e. ( _Left ` 0s ) d = ( ( ( v x.s 0s ) +s ( A x.s w ) ) -s ( v x.s w ) ) } ) = ( (/) u. (/) ) | 
						
						
							| 34 | 
							
								33 19
							 | 
							eqtri | 
							 |-  ( { c | E. t e. ( _Left ` A ) E. u e. ( _Right ` 0s ) c = ( ( ( t x.s 0s ) +s ( A x.s u ) ) -s ( t x.s u ) ) } u. { d | E. v e. ( _Right ` A ) E. w e. ( _Left ` 0s ) d = ( ( ( v x.s 0s ) +s ( A x.s w ) ) -s ( v x.s w ) ) } ) = (/) | 
						
						
							| 35 | 
							
								20 34
							 | 
							oveq12i | 
							 |-  ( ( { a | E. p e. ( _Left ` A ) E. q e. ( _Left ` 0s ) a = ( ( ( p x.s 0s ) +s ( A x.s q ) ) -s ( p x.s q ) ) } u. { b | E. r e. ( _Right ` A ) E. s e. ( _Right ` 0s ) b = ( ( ( r x.s 0s ) +s ( A x.s s ) ) -s ( r x.s s ) ) } ) |s ( { c | E. t e. ( _Left ` A ) E. u e. ( _Right ` 0s ) c = ( ( ( t x.s 0s ) +s ( A x.s u ) ) -s ( t x.s u ) ) } u. { d | E. v e. ( _Right ` A ) E. w e. ( _Left ` 0s ) d = ( ( ( v x.s 0s ) +s ( A x.s w ) ) -s ( v x.s w ) ) } ) ) = ( (/) |s (/) ) | 
						
						
							| 36 | 
							
								
							 | 
							df-0s | 
							 |-  0s = ( (/) |s (/) )  | 
						
						
							| 37 | 
							
								35 36
							 | 
							eqtr4i | 
							 |-  ( ( { a | E. p e. ( _Left ` A ) E. q e. ( _Left ` 0s ) a = ( ( ( p x.s 0s ) +s ( A x.s q ) ) -s ( p x.s q ) ) } u. { b | E. r e. ( _Right ` A ) E. s e. ( _Right ` 0s ) b = ( ( ( r x.s 0s ) +s ( A x.s s ) ) -s ( r x.s s ) ) } ) |s ( { c | E. t e. ( _Left ` A ) E. u e. ( _Right ` 0s ) c = ( ( ( t x.s 0s ) +s ( A x.s u ) ) -s ( t x.s u ) ) } u. { d | E. v e. ( _Right ` A ) E. w e. ( _Left ` 0s ) d = ( ( ( v x.s 0s ) +s ( A x.s w ) ) -s ( v x.s w ) ) } ) ) = 0s | 
						
						
							| 38 | 
							
								3 37
							 | 
							eqtrdi | 
							 |-  ( A e. No -> ( A x.s 0s ) = 0s )  |