| Step | Hyp | Ref | Expression | 
						
							| 1 |  | opsbc2ie.a |  |-  ( p = <. a , b >. -> ( ph <-> ch ) ) | 
						
							| 2 | 1 | sbcth |  |-  ( x e. _V -> [. x / a ]. ( p = <. a , b >. -> ( ph <-> ch ) ) ) | 
						
							| 3 |  | sbcim1 |  |-  ( [. x / a ]. ( p = <. a , b >. -> ( ph <-> ch ) ) -> ( [. x / a ]. p = <. a , b >. -> [. x / a ]. ( ph <-> ch ) ) ) | 
						
							| 4 | 2 3 | syl |  |-  ( x e. _V -> ( [. x / a ]. p = <. a , b >. -> [. x / a ]. ( ph <-> ch ) ) ) | 
						
							| 5 |  | sbceq2g |  |-  ( x e. _V -> ( [. x / a ]. p = <. a , b >. <-> p = [_ x / a ]_ <. a , b >. ) ) | 
						
							| 6 |  | csbopg |  |-  ( x e. _V -> [_ x / a ]_ <. a , b >. = <. [_ x / a ]_ a , [_ x / a ]_ b >. ) | 
						
							| 7 |  | csbvarg |  |-  ( x e. _V -> [_ x / a ]_ a = x ) | 
						
							| 8 |  | csbconstg |  |-  ( x e. _V -> [_ x / a ]_ b = b ) | 
						
							| 9 | 7 8 | opeq12d |  |-  ( x e. _V -> <. [_ x / a ]_ a , [_ x / a ]_ b >. = <. x , b >. ) | 
						
							| 10 | 6 9 | eqtrd |  |-  ( x e. _V -> [_ x / a ]_ <. a , b >. = <. x , b >. ) | 
						
							| 11 | 10 | eqeq2d |  |-  ( x e. _V -> ( p = [_ x / a ]_ <. a , b >. <-> p = <. x , b >. ) ) | 
						
							| 12 | 5 11 | bitrd |  |-  ( x e. _V -> ( [. x / a ]. p = <. a , b >. <-> p = <. x , b >. ) ) | 
						
							| 13 |  | sbcbig |  |-  ( x e. _V -> ( [. x / a ]. ( ph <-> ch ) <-> ( [. x / a ]. ph <-> [. x / a ]. ch ) ) ) | 
						
							| 14 |  | sbcg |  |-  ( x e. _V -> ( [. x / a ]. ph <-> ph ) ) | 
						
							| 15 | 14 | bibi1d |  |-  ( x e. _V -> ( ( [. x / a ]. ph <-> [. x / a ]. ch ) <-> ( ph <-> [. x / a ]. ch ) ) ) | 
						
							| 16 | 13 15 | bitrd |  |-  ( x e. _V -> ( [. x / a ]. ( ph <-> ch ) <-> ( ph <-> [. x / a ]. ch ) ) ) | 
						
							| 17 | 4 12 16 | 3imtr3d |  |-  ( x e. _V -> ( p = <. x , b >. -> ( ph <-> [. x / a ]. ch ) ) ) | 
						
							| 18 | 17 | elv |  |-  ( p = <. x , b >. -> ( ph <-> [. x / a ]. ch ) ) | 
						
							| 19 | 18 | sbcth |  |-  ( y e. _V -> [. y / b ]. ( p = <. x , b >. -> ( ph <-> [. x / a ]. ch ) ) ) | 
						
							| 20 |  | sbcim1 |  |-  ( [. y / b ]. ( p = <. x , b >. -> ( ph <-> [. x / a ]. ch ) ) -> ( [. y / b ]. p = <. x , b >. -> [. y / b ]. ( ph <-> [. x / a ]. ch ) ) ) | 
						
							| 21 | 19 20 | syl |  |-  ( y e. _V -> ( [. y / b ]. p = <. x , b >. -> [. y / b ]. ( ph <-> [. x / a ]. ch ) ) ) | 
						
							| 22 |  | sbceq2g |  |-  ( y e. _V -> ( [. y / b ]. p = <. x , b >. <-> p = [_ y / b ]_ <. x , b >. ) ) | 
						
							| 23 |  | csbopg |  |-  ( y e. _V -> [_ y / b ]_ <. x , b >. = <. [_ y / b ]_ x , [_ y / b ]_ b >. ) | 
						
							| 24 |  | csbconstg |  |-  ( y e. _V -> [_ y / b ]_ x = x ) | 
						
							| 25 |  | csbvarg |  |-  ( y e. _V -> [_ y / b ]_ b = y ) | 
						
							| 26 | 24 25 | opeq12d |  |-  ( y e. _V -> <. [_ y / b ]_ x , [_ y / b ]_ b >. = <. x , y >. ) | 
						
							| 27 | 23 26 | eqtrd |  |-  ( y e. _V -> [_ y / b ]_ <. x , b >. = <. x , y >. ) | 
						
							| 28 | 27 | eqeq2d |  |-  ( y e. _V -> ( p = [_ y / b ]_ <. x , b >. <-> p = <. x , y >. ) ) | 
						
							| 29 | 22 28 | bitrd |  |-  ( y e. _V -> ( [. y / b ]. p = <. x , b >. <-> p = <. x , y >. ) ) | 
						
							| 30 |  | sbcbig |  |-  ( y e. _V -> ( [. y / b ]. ( ph <-> [. x / a ]. ch ) <-> ( [. y / b ]. ph <-> [. y / b ]. [. x / a ]. ch ) ) ) | 
						
							| 31 |  | sbcg |  |-  ( y e. _V -> ( [. y / b ]. ph <-> ph ) ) | 
						
							| 32 | 31 | bibi1d |  |-  ( y e. _V -> ( ( [. y / b ]. ph <-> [. y / b ]. [. x / a ]. ch ) <-> ( ph <-> [. y / b ]. [. x / a ]. ch ) ) ) | 
						
							| 33 | 30 32 | bitrd |  |-  ( y e. _V -> ( [. y / b ]. ( ph <-> [. x / a ]. ch ) <-> ( ph <-> [. y / b ]. [. x / a ]. ch ) ) ) | 
						
							| 34 | 21 29 33 | 3imtr3d |  |-  ( y e. _V -> ( p = <. x , y >. -> ( ph <-> [. y / b ]. [. x / a ]. ch ) ) ) | 
						
							| 35 | 34 | elv |  |-  ( p = <. x , y >. -> ( ph <-> [. y / b ]. [. x / a ]. ch ) ) |