| Step | Hyp | Ref | Expression | 
						
							| 1 |  | xpss12 | ⊢ ( ( 𝐵  ⊆  𝐷  ∧  𝐴  ⊆  𝐶 )  →  ( 𝐵  ×  𝐴 )  ⊆  ( 𝐷  ×  𝐶 ) ) | 
						
							| 2 | 1 | ancoms | ⊢ ( ( 𝐴  ⊆  𝐶  ∧  𝐵  ⊆  𝐷 )  →  ( 𝐵  ×  𝐴 )  ⊆  ( 𝐷  ×  𝐶 ) ) | 
						
							| 3 |  | sstr | ⊢ ( ( 𝑓  ⊆  ( 𝐵  ×  𝐴 )  ∧  ( 𝐵  ×  𝐴 )  ⊆  ( 𝐷  ×  𝐶 ) )  →  𝑓  ⊆  ( 𝐷  ×  𝐶 ) ) | 
						
							| 4 | 3 | expcom | ⊢ ( ( 𝐵  ×  𝐴 )  ⊆  ( 𝐷  ×  𝐶 )  →  ( 𝑓  ⊆  ( 𝐵  ×  𝐴 )  →  𝑓  ⊆  ( 𝐷  ×  𝐶 ) ) ) | 
						
							| 5 | 2 4 | syl | ⊢ ( ( 𝐴  ⊆  𝐶  ∧  𝐵  ⊆  𝐷 )  →  ( 𝑓  ⊆  ( 𝐵  ×  𝐴 )  →  𝑓  ⊆  ( 𝐷  ×  𝐶 ) ) ) | 
						
							| 6 | 5 | anim2d | ⊢ ( ( 𝐴  ⊆  𝐶  ∧  𝐵  ⊆  𝐷 )  →  ( ( Fun  𝑓  ∧  𝑓  ⊆  ( 𝐵  ×  𝐴 ) )  →  ( Fun  𝑓  ∧  𝑓  ⊆  ( 𝐷  ×  𝐶 ) ) ) ) | 
						
							| 7 | 6 | adantr | ⊢ ( ( ( 𝐴  ⊆  𝐶  ∧  𝐵  ⊆  𝐷 )  ∧  ( 𝐶  ∈  𝑉  ∧  𝐷  ∈  𝑊 ) )  →  ( ( Fun  𝑓  ∧  𝑓  ⊆  ( 𝐵  ×  𝐴 ) )  →  ( Fun  𝑓  ∧  𝑓  ⊆  ( 𝐷  ×  𝐶 ) ) ) ) | 
						
							| 8 |  | ssexg | ⊢ ( ( 𝐴  ⊆  𝐶  ∧  𝐶  ∈  𝑉 )  →  𝐴  ∈  V ) | 
						
							| 9 |  | ssexg | ⊢ ( ( 𝐵  ⊆  𝐷  ∧  𝐷  ∈  𝑊 )  →  𝐵  ∈  V ) | 
						
							| 10 |  | elpmg | ⊢ ( ( 𝐴  ∈  V  ∧  𝐵  ∈  V )  →  ( 𝑓  ∈  ( 𝐴  ↑pm  𝐵 )  ↔  ( Fun  𝑓  ∧  𝑓  ⊆  ( 𝐵  ×  𝐴 ) ) ) ) | 
						
							| 11 | 8 9 10 | syl2an | ⊢ ( ( ( 𝐴  ⊆  𝐶  ∧  𝐶  ∈  𝑉 )  ∧  ( 𝐵  ⊆  𝐷  ∧  𝐷  ∈  𝑊 ) )  →  ( 𝑓  ∈  ( 𝐴  ↑pm  𝐵 )  ↔  ( Fun  𝑓  ∧  𝑓  ⊆  ( 𝐵  ×  𝐴 ) ) ) ) | 
						
							| 12 | 11 | an4s | ⊢ ( ( ( 𝐴  ⊆  𝐶  ∧  𝐵  ⊆  𝐷 )  ∧  ( 𝐶  ∈  𝑉  ∧  𝐷  ∈  𝑊 ) )  →  ( 𝑓  ∈  ( 𝐴  ↑pm  𝐵 )  ↔  ( Fun  𝑓  ∧  𝑓  ⊆  ( 𝐵  ×  𝐴 ) ) ) ) | 
						
							| 13 |  | elpmg | ⊢ ( ( 𝐶  ∈  𝑉  ∧  𝐷  ∈  𝑊 )  →  ( 𝑓  ∈  ( 𝐶  ↑pm  𝐷 )  ↔  ( Fun  𝑓  ∧  𝑓  ⊆  ( 𝐷  ×  𝐶 ) ) ) ) | 
						
							| 14 | 13 | adantl | ⊢ ( ( ( 𝐴  ⊆  𝐶  ∧  𝐵  ⊆  𝐷 )  ∧  ( 𝐶  ∈  𝑉  ∧  𝐷  ∈  𝑊 ) )  →  ( 𝑓  ∈  ( 𝐶  ↑pm  𝐷 )  ↔  ( Fun  𝑓  ∧  𝑓  ⊆  ( 𝐷  ×  𝐶 ) ) ) ) | 
						
							| 15 | 7 12 14 | 3imtr4d | ⊢ ( ( ( 𝐴  ⊆  𝐶  ∧  𝐵  ⊆  𝐷 )  ∧  ( 𝐶  ∈  𝑉  ∧  𝐷  ∈  𝑊 ) )  →  ( 𝑓  ∈  ( 𝐴  ↑pm  𝐵 )  →  𝑓  ∈  ( 𝐶  ↑pm  𝐷 ) ) ) | 
						
							| 16 | 15 | ssrdv | ⊢ ( ( ( 𝐴  ⊆  𝐶  ∧  𝐵  ⊆  𝐷 )  ∧  ( 𝐶  ∈  𝑉  ∧  𝐷  ∈  𝑊 ) )  →  ( 𝐴  ↑pm  𝐵 )  ⊆  ( 𝐶  ↑pm  𝐷 ) ) |