| Step | Hyp | Ref | Expression | 
						
							| 1 |  | xpss12 |  |-  ( ( B C_ D /\ A C_ C ) -> ( B X. A ) C_ ( D X. C ) ) | 
						
							| 2 | 1 | ancoms |  |-  ( ( A C_ C /\ B C_ D ) -> ( B X. A ) C_ ( D X. C ) ) | 
						
							| 3 |  | sstr |  |-  ( ( f C_ ( B X. A ) /\ ( B X. A ) C_ ( D X. C ) ) -> f C_ ( D X. C ) ) | 
						
							| 4 | 3 | expcom |  |-  ( ( B X. A ) C_ ( D X. C ) -> ( f C_ ( B X. A ) -> f C_ ( D X. C ) ) ) | 
						
							| 5 | 2 4 | syl |  |-  ( ( A C_ C /\ B C_ D ) -> ( f C_ ( B X. A ) -> f C_ ( D X. C ) ) ) | 
						
							| 6 | 5 | anim2d |  |-  ( ( A C_ C /\ B C_ D ) -> ( ( Fun f /\ f C_ ( B X. A ) ) -> ( Fun f /\ f C_ ( D X. C ) ) ) ) | 
						
							| 7 | 6 | adantr |  |-  ( ( ( A C_ C /\ B C_ D ) /\ ( C e. V /\ D e. W ) ) -> ( ( Fun f /\ f C_ ( B X. A ) ) -> ( Fun f /\ f C_ ( D X. C ) ) ) ) | 
						
							| 8 |  | ssexg |  |-  ( ( A C_ C /\ C e. V ) -> A e. _V ) | 
						
							| 9 |  | ssexg |  |-  ( ( B C_ D /\ D e. W ) -> B e. _V ) | 
						
							| 10 |  | elpmg |  |-  ( ( A e. _V /\ B e. _V ) -> ( f e. ( A ^pm B ) <-> ( Fun f /\ f C_ ( B X. A ) ) ) ) | 
						
							| 11 | 8 9 10 | syl2an |  |-  ( ( ( A C_ C /\ C e. V ) /\ ( B C_ D /\ D e. W ) ) -> ( f e. ( A ^pm B ) <-> ( Fun f /\ f C_ ( B X. A ) ) ) ) | 
						
							| 12 | 11 | an4s |  |-  ( ( ( A C_ C /\ B C_ D ) /\ ( C e. V /\ D e. W ) ) -> ( f e. ( A ^pm B ) <-> ( Fun f /\ f C_ ( B X. A ) ) ) ) | 
						
							| 13 |  | elpmg |  |-  ( ( C e. V /\ D e. W ) -> ( f e. ( C ^pm D ) <-> ( Fun f /\ f C_ ( D X. C ) ) ) ) | 
						
							| 14 | 13 | adantl |  |-  ( ( ( A C_ C /\ B C_ D ) /\ ( C e. V /\ D e. W ) ) -> ( f e. ( C ^pm D ) <-> ( Fun f /\ f C_ ( D X. C ) ) ) ) | 
						
							| 15 | 7 12 14 | 3imtr4d |  |-  ( ( ( A C_ C /\ B C_ D ) /\ ( C e. V /\ D e. W ) ) -> ( f e. ( A ^pm B ) -> f e. ( C ^pm D ) ) ) | 
						
							| 16 | 15 | ssrdv |  |-  ( ( ( A C_ C /\ B C_ D ) /\ ( C e. V /\ D e. W ) ) -> ( A ^pm B ) C_ ( C ^pm D ) ) |