| Step | Hyp | Ref | Expression | 
						
							| 1 |  | fvex | ⊢ ( 1st  ‘ 𝐴 )  ∈  V | 
						
							| 2 |  | fvex | ⊢ ( 2nd  ‘ 𝐴 )  ∈  V | 
						
							| 3 | 1 2 | unex | ⊢ ( ( 1st  ‘ 𝐴 )  ∪  ( 2nd  ‘ 𝐴 ) )  ∈  V | 
						
							| 4 | 3 | isseti | ⊢ ∃ 𝑥 𝑥  =  ( ( 1st  ‘ 𝐴 )  ∪  ( 2nd  ‘ 𝐴 ) ) | 
						
							| 5 |  | sseq1 | ⊢ ( 𝑥  =  ( ( 1st  ‘ 𝐴 )  ∪  ( 2nd  ‘ 𝐴 ) )  →  ( 𝑥  ⊆  Pg  ↔  ( ( 1st  ‘ 𝐴 )  ∪  ( 2nd  ‘ 𝐴 ) )  ⊆  Pg ) ) | 
						
							| 6 |  | unss | ⊢ ( ( ( 1st  ‘ 𝐴 )  ⊆  Pg  ∧  ( 2nd  ‘ 𝐴 )  ⊆  Pg )  ↔  ( ( 1st  ‘ 𝐴 )  ∪  ( 2nd  ‘ 𝐴 ) )  ⊆  Pg ) | 
						
							| 7 | 5 6 | bitr4di | ⊢ ( 𝑥  =  ( ( 1st  ‘ 𝐴 )  ∪  ( 2nd  ‘ 𝐴 ) )  →  ( 𝑥  ⊆  Pg  ↔  ( ( 1st  ‘ 𝐴 )  ⊆  Pg  ∧  ( 2nd  ‘ 𝐴 )  ⊆  Pg ) ) ) | 
						
							| 8 | 7 | biimprd | ⊢ ( 𝑥  =  ( ( 1st  ‘ 𝐴 )  ∪  ( 2nd  ‘ 𝐴 ) )  →  ( ( ( 1st  ‘ 𝐴 )  ⊆  Pg  ∧  ( 2nd  ‘ 𝐴 )  ⊆  Pg )  →  𝑥  ⊆  Pg ) ) | 
						
							| 9 |  | ssun1 | ⊢ ( 1st  ‘ 𝐴 )  ⊆  ( ( 1st  ‘ 𝐴 )  ∪  ( 2nd  ‘ 𝐴 ) ) | 
						
							| 10 |  | id | ⊢ ( 𝑥  =  ( ( 1st  ‘ 𝐴 )  ∪  ( 2nd  ‘ 𝐴 ) )  →  𝑥  =  ( ( 1st  ‘ 𝐴 )  ∪  ( 2nd  ‘ 𝐴 ) ) ) | 
						
							| 11 | 9 10 | sseqtrrid | ⊢ ( 𝑥  =  ( ( 1st  ‘ 𝐴 )  ∪  ( 2nd  ‘ 𝐴 ) )  →  ( 1st  ‘ 𝐴 )  ⊆  𝑥 ) | 
						
							| 12 |  | vex | ⊢ 𝑥  ∈  V | 
						
							| 13 | 12 | elpw2 | ⊢ ( ( 1st  ‘ 𝐴 )  ∈  𝒫  𝑥  ↔  ( 1st  ‘ 𝐴 )  ⊆  𝑥 ) | 
						
							| 14 | 11 13 | sylibr | ⊢ ( 𝑥  =  ( ( 1st  ‘ 𝐴 )  ∪  ( 2nd  ‘ 𝐴 ) )  →  ( 1st  ‘ 𝐴 )  ∈  𝒫  𝑥 ) | 
						
							| 15 |  | ssun2 | ⊢ ( 2nd  ‘ 𝐴 )  ⊆  ( ( 1st  ‘ 𝐴 )  ∪  ( 2nd  ‘ 𝐴 ) ) | 
						
							| 16 | 15 10 | sseqtrrid | ⊢ ( 𝑥  =  ( ( 1st  ‘ 𝐴 )  ∪  ( 2nd  ‘ 𝐴 ) )  →  ( 2nd  ‘ 𝐴 )  ⊆  𝑥 ) | 
						
							| 17 | 12 | elpw2 | ⊢ ( ( 2nd  ‘ 𝐴 )  ∈  𝒫  𝑥  ↔  ( 2nd  ‘ 𝐴 )  ⊆  𝑥 ) | 
						
							| 18 | 16 17 | sylibr | ⊢ ( 𝑥  =  ( ( 1st  ‘ 𝐴 )  ∪  ( 2nd  ‘ 𝐴 ) )  →  ( 2nd  ‘ 𝐴 )  ∈  𝒫  𝑥 ) | 
						
							| 19 | 14 18 | jca | ⊢ ( 𝑥  =  ( ( 1st  ‘ 𝐴 )  ∪  ( 2nd  ‘ 𝐴 ) )  →  ( ( 1st  ‘ 𝐴 )  ∈  𝒫  𝑥  ∧  ( 2nd  ‘ 𝐴 )  ∈  𝒫  𝑥 ) ) | 
						
							| 20 | 8 19 | jctird | ⊢ ( 𝑥  =  ( ( 1st  ‘ 𝐴 )  ∪  ( 2nd  ‘ 𝐴 ) )  →  ( ( ( 1st  ‘ 𝐴 )  ⊆  Pg  ∧  ( 2nd  ‘ 𝐴 )  ⊆  Pg )  →  ( 𝑥  ⊆  Pg  ∧  ( ( 1st  ‘ 𝐴 )  ∈  𝒫  𝑥  ∧  ( 2nd  ‘ 𝐴 )  ∈  𝒫  𝑥 ) ) ) ) | 
						
							| 21 | 4 20 | eximii | ⊢ ∃ 𝑥 ( ( ( 1st  ‘ 𝐴 )  ⊆  Pg  ∧  ( 2nd  ‘ 𝐴 )  ⊆  Pg )  →  ( 𝑥  ⊆  Pg  ∧  ( ( 1st  ‘ 𝐴 )  ∈  𝒫  𝑥  ∧  ( 2nd  ‘ 𝐴 )  ∈  𝒫  𝑥 ) ) ) | 
						
							| 22 | 21 | 19.37iv | ⊢ ( ( ( 1st  ‘ 𝐴 )  ⊆  Pg  ∧  ( 2nd  ‘ 𝐴 )  ⊆  Pg )  →  ∃ 𝑥 ( 𝑥  ⊆  Pg  ∧  ( ( 1st  ‘ 𝐴 )  ∈  𝒫  𝑥  ∧  ( 2nd  ‘ 𝐴 )  ∈  𝒫  𝑥 ) ) ) |