| Step | Hyp | Ref | Expression | 
						
							| 1 |  | reldom | ⊢ Rel   ≼ | 
						
							| 2 | 1 | brrelex2i | ⊢ ( 𝐴  ≼  𝐵  →  𝐵  ∈  V ) | 
						
							| 3 |  | domeng | ⊢ ( 𝐵  ∈  V  →  ( 𝐴  ≼  𝐵  ↔  ∃ 𝑥 ( 𝐴  ≈  𝑥  ∧  𝑥  ⊆  𝐵 ) ) ) | 
						
							| 4 | 2 3 | syl | ⊢ ( 𝐴  ≼  𝐵  →  ( 𝐴  ≼  𝐵  ↔  ∃ 𝑥 ( 𝐴  ≈  𝑥  ∧  𝑥  ⊆  𝐵 ) ) ) | 
						
							| 5 | 4 | ibi | ⊢ ( 𝐴  ≼  𝐵  →  ∃ 𝑥 ( 𝐴  ≈  𝑥  ∧  𝑥  ⊆  𝐵 ) ) | 
						
							| 6 | 1 | brrelex1i | ⊢ ( 𝐶  ≼  𝐷  →  𝐶  ∈  V ) | 
						
							| 7 |  | difss | ⊢ ( 𝐶  ∖  𝐴 )  ⊆  𝐶 | 
						
							| 8 |  | ssdomg | ⊢ ( 𝐶  ∈  V  →  ( ( 𝐶  ∖  𝐴 )  ⊆  𝐶  →  ( 𝐶  ∖  𝐴 )  ≼  𝐶 ) ) | 
						
							| 9 | 6 7 8 | mpisyl | ⊢ ( 𝐶  ≼  𝐷  →  ( 𝐶  ∖  𝐴 )  ≼  𝐶 ) | 
						
							| 10 |  | domtr | ⊢ ( ( ( 𝐶  ∖  𝐴 )  ≼  𝐶  ∧  𝐶  ≼  𝐷 )  →  ( 𝐶  ∖  𝐴 )  ≼  𝐷 ) | 
						
							| 11 | 9 10 | mpancom | ⊢ ( 𝐶  ≼  𝐷  →  ( 𝐶  ∖  𝐴 )  ≼  𝐷 ) | 
						
							| 12 | 1 | brrelex2i | ⊢ ( ( 𝐶  ∖  𝐴 )  ≼  𝐷  →  𝐷  ∈  V ) | 
						
							| 13 |  | domeng | ⊢ ( 𝐷  ∈  V  →  ( ( 𝐶  ∖  𝐴 )  ≼  𝐷  ↔  ∃ 𝑦 ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) ) ) | 
						
							| 14 | 12 13 | syl | ⊢ ( ( 𝐶  ∖  𝐴 )  ≼  𝐷  →  ( ( 𝐶  ∖  𝐴 )  ≼  𝐷  ↔  ∃ 𝑦 ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) ) ) | 
						
							| 15 | 14 | ibi | ⊢ ( ( 𝐶  ∖  𝐴 )  ≼  𝐷  →  ∃ 𝑦 ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) ) | 
						
							| 16 | 11 15 | syl | ⊢ ( 𝐶  ≼  𝐷  →  ∃ 𝑦 ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) ) | 
						
							| 17 | 5 16 | anim12i | ⊢ ( ( 𝐴  ≼  𝐵  ∧  𝐶  ≼  𝐷 )  →  ( ∃ 𝑥 ( 𝐴  ≈  𝑥  ∧  𝑥  ⊆  𝐵 )  ∧  ∃ 𝑦 ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) ) ) | 
						
							| 18 | 17 | adantr | ⊢ ( ( ( 𝐴  ≼  𝐵  ∧  𝐶  ≼  𝐷 )  ∧  ( 𝐵  ∩  𝐷 )  =  ∅ )  →  ( ∃ 𝑥 ( 𝐴  ≈  𝑥  ∧  𝑥  ⊆  𝐵 )  ∧  ∃ 𝑦 ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) ) ) | 
						
							| 19 |  | exdistrv | ⊢ ( ∃ 𝑥 ∃ 𝑦 ( ( 𝐴  ≈  𝑥  ∧  𝑥  ⊆  𝐵 )  ∧  ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) )  ↔  ( ∃ 𝑥 ( 𝐴  ≈  𝑥  ∧  𝑥  ⊆  𝐵 )  ∧  ∃ 𝑦 ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) ) ) | 
						
							| 20 |  | simprll | ⊢ ( ( ( ( 𝐴  ≼  𝐵  ∧  𝐶  ≼  𝐷 )  ∧  ( 𝐵  ∩  𝐷 )  =  ∅ )  ∧  ( ( 𝐴  ≈  𝑥  ∧  𝑥  ⊆  𝐵 )  ∧  ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) ) )  →  𝐴  ≈  𝑥 ) | 
						
							| 21 |  | simprrl | ⊢ ( ( ( ( 𝐴  ≼  𝐵  ∧  𝐶  ≼  𝐷 )  ∧  ( 𝐵  ∩  𝐷 )  =  ∅ )  ∧  ( ( 𝐴  ≈  𝑥  ∧  𝑥  ⊆  𝐵 )  ∧  ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) ) )  →  ( 𝐶  ∖  𝐴 )  ≈  𝑦 ) | 
						
							| 22 |  | disjdif | ⊢ ( 𝐴  ∩  ( 𝐶  ∖  𝐴 ) )  =  ∅ | 
						
							| 23 | 22 | a1i | ⊢ ( ( ( ( 𝐴  ≼  𝐵  ∧  𝐶  ≼  𝐷 )  ∧  ( 𝐵  ∩  𝐷 )  =  ∅ )  ∧  ( ( 𝐴  ≈  𝑥  ∧  𝑥  ⊆  𝐵 )  ∧  ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) ) )  →  ( 𝐴  ∩  ( 𝐶  ∖  𝐴 ) )  =  ∅ ) | 
						
							| 24 |  | ss2in | ⊢ ( ( 𝑥  ⊆  𝐵  ∧  𝑦  ⊆  𝐷 )  →  ( 𝑥  ∩  𝑦 )  ⊆  ( 𝐵  ∩  𝐷 ) ) | 
						
							| 25 | 24 | ad2ant2l | ⊢ ( ( ( 𝐴  ≈  𝑥  ∧  𝑥  ⊆  𝐵 )  ∧  ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) )  →  ( 𝑥  ∩  𝑦 )  ⊆  ( 𝐵  ∩  𝐷 ) ) | 
						
							| 26 | 25 | adantl | ⊢ ( ( ( ( 𝐴  ≼  𝐵  ∧  𝐶  ≼  𝐷 )  ∧  ( 𝐵  ∩  𝐷 )  =  ∅ )  ∧  ( ( 𝐴  ≈  𝑥  ∧  𝑥  ⊆  𝐵 )  ∧  ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) ) )  →  ( 𝑥  ∩  𝑦 )  ⊆  ( 𝐵  ∩  𝐷 ) ) | 
						
							| 27 |  | simplr | ⊢ ( ( ( ( 𝐴  ≼  𝐵  ∧  𝐶  ≼  𝐷 )  ∧  ( 𝐵  ∩  𝐷 )  =  ∅ )  ∧  ( ( 𝐴  ≈  𝑥  ∧  𝑥  ⊆  𝐵 )  ∧  ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) ) )  →  ( 𝐵  ∩  𝐷 )  =  ∅ ) | 
						
							| 28 |  | sseq0 | ⊢ ( ( ( 𝑥  ∩  𝑦 )  ⊆  ( 𝐵  ∩  𝐷 )  ∧  ( 𝐵  ∩  𝐷 )  =  ∅ )  →  ( 𝑥  ∩  𝑦 )  =  ∅ ) | 
						
							| 29 | 26 27 28 | syl2anc | ⊢ ( ( ( ( 𝐴  ≼  𝐵  ∧  𝐶  ≼  𝐷 )  ∧  ( 𝐵  ∩  𝐷 )  =  ∅ )  ∧  ( ( 𝐴  ≈  𝑥  ∧  𝑥  ⊆  𝐵 )  ∧  ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) ) )  →  ( 𝑥  ∩  𝑦 )  =  ∅ ) | 
						
							| 30 |  | undif2 | ⊢ ( 𝐴  ∪  ( 𝐶  ∖  𝐴 ) )  =  ( 𝐴  ∪  𝐶 ) | 
						
							| 31 |  | unen | ⊢ ( ( ( 𝐴  ≈  𝑥  ∧  ( 𝐶  ∖  𝐴 )  ≈  𝑦 )  ∧  ( ( 𝐴  ∩  ( 𝐶  ∖  𝐴 ) )  =  ∅  ∧  ( 𝑥  ∩  𝑦 )  =  ∅ ) )  →  ( 𝐴  ∪  ( 𝐶  ∖  𝐴 ) )  ≈  ( 𝑥  ∪  𝑦 ) ) | 
						
							| 32 | 30 31 | eqbrtrrid | ⊢ ( ( ( 𝐴  ≈  𝑥  ∧  ( 𝐶  ∖  𝐴 )  ≈  𝑦 )  ∧  ( ( 𝐴  ∩  ( 𝐶  ∖  𝐴 ) )  =  ∅  ∧  ( 𝑥  ∩  𝑦 )  =  ∅ ) )  →  ( 𝐴  ∪  𝐶 )  ≈  ( 𝑥  ∪  𝑦 ) ) | 
						
							| 33 | 20 21 23 29 32 | syl22anc | ⊢ ( ( ( ( 𝐴  ≼  𝐵  ∧  𝐶  ≼  𝐷 )  ∧  ( 𝐵  ∩  𝐷 )  =  ∅ )  ∧  ( ( 𝐴  ≈  𝑥  ∧  𝑥  ⊆  𝐵 )  ∧  ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) ) )  →  ( 𝐴  ∪  𝐶 )  ≈  ( 𝑥  ∪  𝑦 ) ) | 
						
							| 34 | 2 | ad3antrrr | ⊢ ( ( ( ( 𝐴  ≼  𝐵  ∧  𝐶  ≼  𝐷 )  ∧  ( 𝐵  ∩  𝐷 )  =  ∅ )  ∧  ( ( 𝐴  ≈  𝑥  ∧  𝑥  ⊆  𝐵 )  ∧  ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) ) )  →  𝐵  ∈  V ) | 
						
							| 35 | 1 | brrelex2i | ⊢ ( 𝐶  ≼  𝐷  →  𝐷  ∈  V ) | 
						
							| 36 | 35 | ad3antlr | ⊢ ( ( ( ( 𝐴  ≼  𝐵  ∧  𝐶  ≼  𝐷 )  ∧  ( 𝐵  ∩  𝐷 )  =  ∅ )  ∧  ( ( 𝐴  ≈  𝑥  ∧  𝑥  ⊆  𝐵 )  ∧  ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) ) )  →  𝐷  ∈  V ) | 
						
							| 37 |  | unexg | ⊢ ( ( 𝐵  ∈  V  ∧  𝐷  ∈  V )  →  ( 𝐵  ∪  𝐷 )  ∈  V ) | 
						
							| 38 | 34 36 37 | syl2anc | ⊢ ( ( ( ( 𝐴  ≼  𝐵  ∧  𝐶  ≼  𝐷 )  ∧  ( 𝐵  ∩  𝐷 )  =  ∅ )  ∧  ( ( 𝐴  ≈  𝑥  ∧  𝑥  ⊆  𝐵 )  ∧  ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) ) )  →  ( 𝐵  ∪  𝐷 )  ∈  V ) | 
						
							| 39 |  | unss12 | ⊢ ( ( 𝑥  ⊆  𝐵  ∧  𝑦  ⊆  𝐷 )  →  ( 𝑥  ∪  𝑦 )  ⊆  ( 𝐵  ∪  𝐷 ) ) | 
						
							| 40 | 39 | ad2ant2l | ⊢ ( ( ( 𝐴  ≈  𝑥  ∧  𝑥  ⊆  𝐵 )  ∧  ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) )  →  ( 𝑥  ∪  𝑦 )  ⊆  ( 𝐵  ∪  𝐷 ) ) | 
						
							| 41 | 40 | adantl | ⊢ ( ( ( ( 𝐴  ≼  𝐵  ∧  𝐶  ≼  𝐷 )  ∧  ( 𝐵  ∩  𝐷 )  =  ∅ )  ∧  ( ( 𝐴  ≈  𝑥  ∧  𝑥  ⊆  𝐵 )  ∧  ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) ) )  →  ( 𝑥  ∪  𝑦 )  ⊆  ( 𝐵  ∪  𝐷 ) ) | 
						
							| 42 |  | ssdomg | ⊢ ( ( 𝐵  ∪  𝐷 )  ∈  V  →  ( ( 𝑥  ∪  𝑦 )  ⊆  ( 𝐵  ∪  𝐷 )  →  ( 𝑥  ∪  𝑦 )  ≼  ( 𝐵  ∪  𝐷 ) ) ) | 
						
							| 43 | 38 41 42 | sylc | ⊢ ( ( ( ( 𝐴  ≼  𝐵  ∧  𝐶  ≼  𝐷 )  ∧  ( 𝐵  ∩  𝐷 )  =  ∅ )  ∧  ( ( 𝐴  ≈  𝑥  ∧  𝑥  ⊆  𝐵 )  ∧  ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) ) )  →  ( 𝑥  ∪  𝑦 )  ≼  ( 𝐵  ∪  𝐷 ) ) | 
						
							| 44 |  | endomtr | ⊢ ( ( ( 𝐴  ∪  𝐶 )  ≈  ( 𝑥  ∪  𝑦 )  ∧  ( 𝑥  ∪  𝑦 )  ≼  ( 𝐵  ∪  𝐷 ) )  →  ( 𝐴  ∪  𝐶 )  ≼  ( 𝐵  ∪  𝐷 ) ) | 
						
							| 45 | 33 43 44 | syl2anc | ⊢ ( ( ( ( 𝐴  ≼  𝐵  ∧  𝐶  ≼  𝐷 )  ∧  ( 𝐵  ∩  𝐷 )  =  ∅ )  ∧  ( ( 𝐴  ≈  𝑥  ∧  𝑥  ⊆  𝐵 )  ∧  ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) ) )  →  ( 𝐴  ∪  𝐶 )  ≼  ( 𝐵  ∪  𝐷 ) ) | 
						
							| 46 | 45 | ex | ⊢ ( ( ( 𝐴  ≼  𝐵  ∧  𝐶  ≼  𝐷 )  ∧  ( 𝐵  ∩  𝐷 )  =  ∅ )  →  ( ( ( 𝐴  ≈  𝑥  ∧  𝑥  ⊆  𝐵 )  ∧  ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) )  →  ( 𝐴  ∪  𝐶 )  ≼  ( 𝐵  ∪  𝐷 ) ) ) | 
						
							| 47 | 46 | exlimdvv | ⊢ ( ( ( 𝐴  ≼  𝐵  ∧  𝐶  ≼  𝐷 )  ∧  ( 𝐵  ∩  𝐷 )  =  ∅ )  →  ( ∃ 𝑥 ∃ 𝑦 ( ( 𝐴  ≈  𝑥  ∧  𝑥  ⊆  𝐵 )  ∧  ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) )  →  ( 𝐴  ∪  𝐶 )  ≼  ( 𝐵  ∪  𝐷 ) ) ) | 
						
							| 48 | 19 47 | biimtrrid | ⊢ ( ( ( 𝐴  ≼  𝐵  ∧  𝐶  ≼  𝐷 )  ∧  ( 𝐵  ∩  𝐷 )  =  ∅ )  →  ( ( ∃ 𝑥 ( 𝐴  ≈  𝑥  ∧  𝑥  ⊆  𝐵 )  ∧  ∃ 𝑦 ( ( 𝐶  ∖  𝐴 )  ≈  𝑦  ∧  𝑦  ⊆  𝐷 ) )  →  ( 𝐴  ∪  𝐶 )  ≼  ( 𝐵  ∪  𝐷 ) ) ) | 
						
							| 49 | 18 48 | mpd | ⊢ ( ( ( 𝐴  ≼  𝐵  ∧  𝐶  ≼  𝐷 )  ∧  ( 𝐵  ∩  𝐷 )  =  ∅ )  →  ( 𝐴  ∪  𝐶 )  ≼  ( 𝐵  ∪  𝐷 ) ) |