| Step | Hyp | Ref | Expression | 
						
							| 1 |  | biimp |  |-  ( ( ( u X. { x } ) C_ M <-> ( u X. { t } ) C_ M ) -> ( ( u X. { x } ) C_ M -> ( u X. { t } ) C_ M ) ) | 
						
							| 2 |  | iitop |  |-  II e. Top | 
						
							| 3 |  | iiuni |  |-  ( 0 [,] 1 ) = U. II | 
						
							| 4 | 3 | neii1 |  |-  ( ( II e. Top /\ u e. ( ( nei ` II ) ` { y } ) ) -> u C_ ( 0 [,] 1 ) ) | 
						
							| 5 | 2 4 | mpan |  |-  ( u e. ( ( nei ` II ) ` { y } ) -> u C_ ( 0 [,] 1 ) ) | 
						
							| 6 | 5 | adantl |  |-  ( ( ( ( 0 [,] 1 ) X. { x } ) C_ M /\ u e. ( ( nei ` II ) ` { y } ) ) -> u C_ ( 0 [,] 1 ) ) | 
						
							| 7 |  | xpss1 |  |-  ( u C_ ( 0 [,] 1 ) -> ( u X. { x } ) C_ ( ( 0 [,] 1 ) X. { x } ) ) | 
						
							| 8 | 6 7 | syl |  |-  ( ( ( ( 0 [,] 1 ) X. { x } ) C_ M /\ u e. ( ( nei ` II ) ` { y } ) ) -> ( u X. { x } ) C_ ( ( 0 [,] 1 ) X. { x } ) ) | 
						
							| 9 |  | simpl |  |-  ( ( ( ( 0 [,] 1 ) X. { x } ) C_ M /\ u e. ( ( nei ` II ) ` { y } ) ) -> ( ( 0 [,] 1 ) X. { x } ) C_ M ) | 
						
							| 10 | 8 9 | sstrd |  |-  ( ( ( ( 0 [,] 1 ) X. { x } ) C_ M /\ u e. ( ( nei ` II ) ` { y } ) ) -> ( u X. { x } ) C_ M ) | 
						
							| 11 |  | ssnei |  |-  ( ( II e. Top /\ u e. ( ( nei ` II ) ` { y } ) ) -> { y } C_ u ) | 
						
							| 12 | 2 11 | mpan |  |-  ( u e. ( ( nei ` II ) ` { y } ) -> { y } C_ u ) | 
						
							| 13 | 12 | adantl |  |-  ( ( ( ( 0 [,] 1 ) X. { x } ) C_ M /\ u e. ( ( nei ` II ) ` { y } ) ) -> { y } C_ u ) | 
						
							| 14 |  | vex |  |-  y e. _V | 
						
							| 15 | 14 | snss |  |-  ( y e. u <-> { y } C_ u ) | 
						
							| 16 | 13 15 | sylibr |  |-  ( ( ( ( 0 [,] 1 ) X. { x } ) C_ M /\ u e. ( ( nei ` II ) ` { y } ) ) -> y e. u ) | 
						
							| 17 |  | vsnid |  |-  t e. { t } | 
						
							| 18 |  | opelxpi |  |-  ( ( y e. u /\ t e. { t } ) -> <. y , t >. e. ( u X. { t } ) ) | 
						
							| 19 | 16 17 18 | sylancl |  |-  ( ( ( ( 0 [,] 1 ) X. { x } ) C_ M /\ u e. ( ( nei ` II ) ` { y } ) ) -> <. y , t >. e. ( u X. { t } ) ) | 
						
							| 20 |  | ssel |  |-  ( ( u X. { t } ) C_ M -> ( <. y , t >. e. ( u X. { t } ) -> <. y , t >. e. M ) ) | 
						
							| 21 | 19 20 | syl5com |  |-  ( ( ( ( 0 [,] 1 ) X. { x } ) C_ M /\ u e. ( ( nei ` II ) ` { y } ) ) -> ( ( u X. { t } ) C_ M -> <. y , t >. e. M ) ) | 
						
							| 22 | 10 21 | embantd |  |-  ( ( ( ( 0 [,] 1 ) X. { x } ) C_ M /\ u e. ( ( nei ` II ) ` { y } ) ) -> ( ( ( u X. { x } ) C_ M -> ( u X. { t } ) C_ M ) -> <. y , t >. e. M ) ) | 
						
							| 23 | 1 22 | syl5 |  |-  ( ( ( ( 0 [,] 1 ) X. { x } ) C_ M /\ u e. ( ( nei ` II ) ` { y } ) ) -> ( ( ( u X. { x } ) C_ M <-> ( u X. { t } ) C_ M ) -> <. y , t >. e. M ) ) | 
						
							| 24 | 23 | rexlimdva |  |-  ( ( ( 0 [,] 1 ) X. { x } ) C_ M -> ( E. u e. ( ( nei ` II ) ` { y } ) ( ( u X. { x } ) C_ M <-> ( u X. { t } ) C_ M ) -> <. y , t >. e. M ) ) | 
						
							| 25 | 24 | ralimdv |  |-  ( ( ( 0 [,] 1 ) X. { x } ) C_ M -> ( A. y e. ( 0 [,] 1 ) E. u e. ( ( nei ` II ) ` { y } ) ( ( u X. { x } ) C_ M <-> ( u X. { t } ) C_ M ) -> A. y e. ( 0 [,] 1 ) <. y , t >. e. M ) ) | 
						
							| 26 | 25 | com12 |  |-  ( A. y e. ( 0 [,] 1 ) E. u e. ( ( nei ` II ) ` { y } ) ( ( u X. { x } ) C_ M <-> ( u X. { t } ) C_ M ) -> ( ( ( 0 [,] 1 ) X. { x } ) C_ M -> A. y e. ( 0 [,] 1 ) <. y , t >. e. M ) ) | 
						
							| 27 |  | dfss3 |  |-  ( ( ( 0 [,] 1 ) X. { t } ) C_ M <-> A. z e. ( ( 0 [,] 1 ) X. { t } ) z e. M ) | 
						
							| 28 |  | eleq1 |  |-  ( z = <. y , u >. -> ( z e. M <-> <. y , u >. e. M ) ) | 
						
							| 29 | 28 | ralxp |  |-  ( A. z e. ( ( 0 [,] 1 ) X. { t } ) z e. M <-> A. y e. ( 0 [,] 1 ) A. u e. { t } <. y , u >. e. M ) | 
						
							| 30 |  | vex |  |-  t e. _V | 
						
							| 31 |  | opeq2 |  |-  ( u = t -> <. y , u >. = <. y , t >. ) | 
						
							| 32 | 31 | eleq1d |  |-  ( u = t -> ( <. y , u >. e. M <-> <. y , t >. e. M ) ) | 
						
							| 33 | 30 32 | ralsn |  |-  ( A. u e. { t } <. y , u >. e. M <-> <. y , t >. e. M ) | 
						
							| 34 | 33 | ralbii |  |-  ( A. y e. ( 0 [,] 1 ) A. u e. { t } <. y , u >. e. M <-> A. y e. ( 0 [,] 1 ) <. y , t >. e. M ) | 
						
							| 35 | 27 29 34 | 3bitri |  |-  ( ( ( 0 [,] 1 ) X. { t } ) C_ M <-> A. y e. ( 0 [,] 1 ) <. y , t >. e. M ) | 
						
							| 36 | 26 35 | imbitrrdi |  |-  ( A. y e. ( 0 [,] 1 ) E. u e. ( ( nei ` II ) ` { y } ) ( ( u X. { x } ) C_ M <-> ( u X. { t } ) C_ M ) -> ( ( ( 0 [,] 1 ) X. { x } ) C_ M -> ( ( 0 [,] 1 ) X. { t } ) C_ M ) ) |