| Step | 
						Hyp | 
						Ref | 
						Expression | 
					
						
							| 1 | 
							
								
							 | 
							chsscon3 | 
							⊢ ( ( 𝐴  ∈   Cℋ   ∧  𝐵  ∈   Cℋ  )  →  ( 𝐴  ⊆  𝐵  ↔  ( ⊥ ‘ 𝐵 )  ⊆  ( ⊥ ‘ 𝐴 ) ) )  | 
						
						
							| 2 | 
							
								
							 | 
							chsscon3 | 
							⊢ ( ( 𝐵  ∈   Cℋ   ∧  𝐴  ∈   Cℋ  )  →  ( 𝐵  ⊆  𝐴  ↔  ( ⊥ ‘ 𝐴 )  ⊆  ( ⊥ ‘ 𝐵 ) ) )  | 
						
						
							| 3 | 
							
								2
							 | 
							ancoms | 
							⊢ ( ( 𝐴  ∈   Cℋ   ∧  𝐵  ∈   Cℋ  )  →  ( 𝐵  ⊆  𝐴  ↔  ( ⊥ ‘ 𝐴 )  ⊆  ( ⊥ ‘ 𝐵 ) ) )  | 
						
						
							| 4 | 
							
								3
							 | 
							notbid | 
							⊢ ( ( 𝐴  ∈   Cℋ   ∧  𝐵  ∈   Cℋ  )  →  ( ¬  𝐵  ⊆  𝐴  ↔  ¬  ( ⊥ ‘ 𝐴 )  ⊆  ( ⊥ ‘ 𝐵 ) ) )  | 
						
						
							| 5 | 
							
								1 4
							 | 
							anbi12d | 
							⊢ ( ( 𝐴  ∈   Cℋ   ∧  𝐵  ∈   Cℋ  )  →  ( ( 𝐴  ⊆  𝐵  ∧  ¬  𝐵  ⊆  𝐴 )  ↔  ( ( ⊥ ‘ 𝐵 )  ⊆  ( ⊥ ‘ 𝐴 )  ∧  ¬  ( ⊥ ‘ 𝐴 )  ⊆  ( ⊥ ‘ 𝐵 ) ) ) )  | 
						
						
							| 6 | 
							
								
							 | 
							dfpss3 | 
							⊢ ( 𝐴  ⊊  𝐵  ↔  ( 𝐴  ⊆  𝐵  ∧  ¬  𝐵  ⊆  𝐴 ) )  | 
						
						
							| 7 | 
							
								
							 | 
							dfpss3 | 
							⊢ ( ( ⊥ ‘ 𝐵 )  ⊊  ( ⊥ ‘ 𝐴 )  ↔  ( ( ⊥ ‘ 𝐵 )  ⊆  ( ⊥ ‘ 𝐴 )  ∧  ¬  ( ⊥ ‘ 𝐴 )  ⊆  ( ⊥ ‘ 𝐵 ) ) )  | 
						
						
							| 8 | 
							
								5 6 7
							 | 
							3bitr4g | 
							⊢ ( ( 𝐴  ∈   Cℋ   ∧  𝐵  ∈   Cℋ  )  →  ( 𝐴  ⊊  𝐵  ↔  ( ⊥ ‘ 𝐵 )  ⊊  ( ⊥ ‘ 𝐴 ) ) )  |