| Step | Hyp | Ref | Expression | 
						
							| 1 |  | idn1 |  |-  (. A e. B ->. A e. B ). | 
						
							| 2 |  | sbcor |  |-  ( [. A / x ]. ( ( ph \/ ps ) \/ ch ) <-> ( [. A / x ]. ( ph \/ ps ) \/ [. A / x ]. ch ) ) | 
						
							| 3 | 2 | a1i |  |-  ( A e. B -> ( [. A / x ]. ( ( ph \/ ps ) \/ ch ) <-> ( [. A / x ]. ( ph \/ ps ) \/ [. A / x ]. ch ) ) ) | 
						
							| 4 | 1 3 | e1a |  |-  (. A e. B ->. ( [. A / x ]. ( ( ph \/ ps ) \/ ch ) <-> ( [. A / x ]. ( ph \/ ps ) \/ [. A / x ]. ch ) ) ). | 
						
							| 5 |  | df-3or |  |-  ( ( ph \/ ps \/ ch ) <-> ( ( ph \/ ps ) \/ ch ) ) | 
						
							| 6 | 5 | bicomi |  |-  ( ( ( ph \/ ps ) \/ ch ) <-> ( ph \/ ps \/ ch ) ) | 
						
							| 7 | 6 | ax-gen |  |-  A. x ( ( ( ph \/ ps ) \/ ch ) <-> ( ph \/ ps \/ ch ) ) | 
						
							| 8 |  | spsbc |  |-  ( A e. B -> ( A. x ( ( ( ph \/ ps ) \/ ch ) <-> ( ph \/ ps \/ ch ) ) -> [. A / x ]. ( ( ( ph \/ ps ) \/ ch ) <-> ( ph \/ ps \/ ch ) ) ) ) | 
						
							| 9 | 1 7 8 | e10 |  |-  (. A e. B ->. [. A / x ]. ( ( ( ph \/ ps ) \/ ch ) <-> ( ph \/ ps \/ ch ) ) ). | 
						
							| 10 |  | sbcbig |  |-  ( A e. B -> ( [. A / x ]. ( ( ( ph \/ ps ) \/ ch ) <-> ( ph \/ ps \/ ch ) ) <-> ( [. A / x ]. ( ( ph \/ ps ) \/ ch ) <-> [. A / x ]. ( ph \/ ps \/ ch ) ) ) ) | 
						
							| 11 | 10 | biimpd |  |-  ( A e. B -> ( [. A / x ]. ( ( ( ph \/ ps ) \/ ch ) <-> ( ph \/ ps \/ ch ) ) -> ( [. A / x ]. ( ( ph \/ ps ) \/ ch ) <-> [. A / x ]. ( ph \/ ps \/ ch ) ) ) ) | 
						
							| 12 | 1 9 11 | e11 |  |-  (. A e. B ->. ( [. A / x ]. ( ( ph \/ ps ) \/ ch ) <-> [. A / x ]. ( ph \/ ps \/ ch ) ) ). | 
						
							| 13 |  | bitr3 |  |-  ( ( [. A / x ]. ( ( ph \/ ps ) \/ ch ) <-> [. A / x ]. ( ph \/ ps \/ ch ) ) -> ( ( [. A / x ]. ( ( ph \/ ps ) \/ ch ) <-> ( [. A / x ]. ( ph \/ ps ) \/ [. A / x ]. ch ) ) -> ( [. A / x ]. ( ph \/ ps \/ ch ) <-> ( [. A / x ]. ( ph \/ ps ) \/ [. A / x ]. ch ) ) ) ) | 
						
							| 14 | 13 | com12 |  |-  ( ( [. A / x ]. ( ( ph \/ ps ) \/ ch ) <-> ( [. A / x ]. ( ph \/ ps ) \/ [. A / x ]. ch ) ) -> ( ( [. A / x ]. ( ( ph \/ ps ) \/ ch ) <-> [. A / x ]. ( ph \/ ps \/ ch ) ) -> ( [. A / x ]. ( ph \/ ps \/ ch ) <-> ( [. A / x ]. ( ph \/ ps ) \/ [. A / x ]. ch ) ) ) ) | 
						
							| 15 | 4 12 14 | e11 |  |-  (. A e. B ->. ( [. A / x ]. ( ph \/ ps \/ ch ) <-> ( [. A / x ]. ( ph \/ ps ) \/ [. A / x ]. ch ) ) ). | 
						
							| 16 |  | sbcor |  |-  ( [. A / x ]. ( ph \/ ps ) <-> ( [. A / x ]. ph \/ [. A / x ]. ps ) ) | 
						
							| 17 | 16 | a1i |  |-  ( A e. B -> ( [. A / x ]. ( ph \/ ps ) <-> ( [. A / x ]. ph \/ [. A / x ]. ps ) ) ) | 
						
							| 18 | 1 17 | e1a |  |-  (. A e. B ->. ( [. A / x ]. ( ph \/ ps ) <-> ( [. A / x ]. ph \/ [. A / x ]. ps ) ) ). | 
						
							| 19 |  | orbi1 |  |-  ( ( [. A / x ]. ( ph \/ ps ) <-> ( [. A / x ]. ph \/ [. A / x ]. ps ) ) -> ( ( [. A / x ]. ( ph \/ ps ) \/ [. A / x ]. ch ) <-> ( ( [. A / x ]. ph \/ [. A / x ]. ps ) \/ [. A / x ]. ch ) ) ) | 
						
							| 20 | 18 19 | e1a |  |-  (. A e. B ->. ( ( [. A / x ]. ( ph \/ ps ) \/ [. A / x ]. ch ) <-> ( ( [. A / x ]. ph \/ [. A / x ]. ps ) \/ [. A / x ]. ch ) ) ). | 
						
							| 21 |  | bibi1 |  |-  ( ( [. A / x ]. ( ph \/ ps \/ ch ) <-> ( [. A / x ]. ( ph \/ ps ) \/ [. A / x ]. ch ) ) -> ( ( [. A / x ]. ( ph \/ ps \/ ch ) <-> ( ( [. A / x ]. ph \/ [. A / x ]. ps ) \/ [. A / x ]. ch ) ) <-> ( ( [. A / x ]. ( ph \/ ps ) \/ [. A / x ]. ch ) <-> ( ( [. A / x ]. ph \/ [. A / x ]. ps ) \/ [. A / x ]. ch ) ) ) ) | 
						
							| 22 | 21 | biimprd |  |-  ( ( [. A / x ]. ( ph \/ ps \/ ch ) <-> ( [. A / x ]. ( ph \/ ps ) \/ [. A / x ]. ch ) ) -> ( ( ( [. A / x ]. ( ph \/ ps ) \/ [. A / x ]. ch ) <-> ( ( [. A / x ]. ph \/ [. A / x ]. ps ) \/ [. A / x ]. ch ) ) -> ( [. A / x ]. ( ph \/ ps \/ ch ) <-> ( ( [. A / x ]. ph \/ [. A / x ]. ps ) \/ [. A / x ]. ch ) ) ) ) | 
						
							| 23 | 15 20 22 | e11 |  |-  (. A e. B ->. ( [. A / x ]. ( ph \/ ps \/ ch ) <-> ( ( [. A / x ]. ph \/ [. A / x ]. ps ) \/ [. A / x ]. ch ) ) ). | 
						
							| 24 |  | df-3or |  |-  ( ( [. A / x ]. ph \/ [. A / x ]. ps \/ [. A / x ]. ch ) <-> ( ( [. A / x ]. ph \/ [. A / x ]. ps ) \/ [. A / x ]. ch ) ) | 
						
							| 25 | 24 | bicomi |  |-  ( ( ( [. A / x ]. ph \/ [. A / x ]. ps ) \/ [. A / x ]. ch ) <-> ( [. A / x ]. ph \/ [. A / x ]. ps \/ [. A / x ]. ch ) ) | 
						
							| 26 |  | bibi1 |  |-  ( ( [. A / x ]. ( ph \/ ps \/ ch ) <-> ( ( [. A / x ]. ph \/ [. A / x ]. ps ) \/ [. A / x ]. ch ) ) -> ( ( [. A / x ]. ( ph \/ ps \/ ch ) <-> ( [. A / x ]. ph \/ [. A / x ]. ps \/ [. A / x ]. ch ) ) <-> ( ( ( [. A / x ]. ph \/ [. A / x ]. ps ) \/ [. A / x ]. ch ) <-> ( [. A / x ]. ph \/ [. A / x ]. ps \/ [. A / x ]. ch ) ) ) ) | 
						
							| 27 | 26 | biimprd |  |-  ( ( [. A / x ]. ( ph \/ ps \/ ch ) <-> ( ( [. A / x ]. ph \/ [. A / x ]. ps ) \/ [. A / x ]. ch ) ) -> ( ( ( ( [. A / x ]. ph \/ [. A / x ]. ps ) \/ [. A / x ]. ch ) <-> ( [. A / x ]. ph \/ [. A / x ]. ps \/ [. A / x ]. ch ) ) -> ( [. A / x ]. ( ph \/ ps \/ ch ) <-> ( [. A / x ]. ph \/ [. A / x ]. ps \/ [. A / x ]. ch ) ) ) ) | 
						
							| 28 | 23 25 27 | e10 |  |-  (. A e. B ->. ( [. A / x ]. ( ph \/ ps \/ ch ) <-> ( [. A / x ]. ph \/ [. A / x ]. ps \/ [. A / x ]. ch ) ) ). | 
						
							| 29 | 28 | in1 |  |-  ( A e. B -> ( [. A / x ]. ( ph \/ ps \/ ch ) <-> ( [. A / x ]. ph \/ [. A / x ]. ps \/ [. A / x ]. ch ) ) ) |