| Step | 
						Hyp | 
						Ref | 
						Expression | 
					
						
							| 1 | 
							
								
							 | 
							pclss.a | 
							⊢ 𝐴  =  ( Atoms ‘ 𝐾 )  | 
						
						
							| 2 | 
							
								
							 | 
							pclss.c | 
							⊢ 𝑈  =  ( PCl ‘ 𝐾 )  | 
						
						
							| 3 | 
							
								
							 | 
							sstr2 | 
							⊢ ( 𝑋  ⊆  𝑌  →  ( 𝑌  ⊆  𝑦  →  𝑋  ⊆  𝑦 ) )  | 
						
						
							| 4 | 
							
								3
							 | 
							3ad2ant2 | 
							⊢ ( ( 𝐾  ∈  𝑉  ∧  𝑋  ⊆  𝑌  ∧  𝑌  ⊆  𝐴 )  →  ( 𝑌  ⊆  𝑦  →  𝑋  ⊆  𝑦 ) )  | 
						
						
							| 5 | 
							
								4
							 | 
							adantr | 
							⊢ ( ( ( 𝐾  ∈  𝑉  ∧  𝑋  ⊆  𝑌  ∧  𝑌  ⊆  𝐴 )  ∧  𝑦  ∈  ( PSubSp ‘ 𝐾 ) )  →  ( 𝑌  ⊆  𝑦  →  𝑋  ⊆  𝑦 ) )  | 
						
						
							| 6 | 
							
								5
							 | 
							ss2rabdv | 
							⊢ ( ( 𝐾  ∈  𝑉  ∧  𝑋  ⊆  𝑌  ∧  𝑌  ⊆  𝐴 )  →  { 𝑦  ∈  ( PSubSp ‘ 𝐾 )  ∣  𝑌  ⊆  𝑦 }  ⊆  { 𝑦  ∈  ( PSubSp ‘ 𝐾 )  ∣  𝑋  ⊆  𝑦 } )  | 
						
						
							| 7 | 
							
								
							 | 
							intss | 
							⊢ ( { 𝑦  ∈  ( PSubSp ‘ 𝐾 )  ∣  𝑌  ⊆  𝑦 }  ⊆  { 𝑦  ∈  ( PSubSp ‘ 𝐾 )  ∣  𝑋  ⊆  𝑦 }  →  ∩  { 𝑦  ∈  ( PSubSp ‘ 𝐾 )  ∣  𝑋  ⊆  𝑦 }  ⊆  ∩  { 𝑦  ∈  ( PSubSp ‘ 𝐾 )  ∣  𝑌  ⊆  𝑦 } )  | 
						
						
							| 8 | 
							
								6 7
							 | 
							syl | 
							⊢ ( ( 𝐾  ∈  𝑉  ∧  𝑋  ⊆  𝑌  ∧  𝑌  ⊆  𝐴 )  →  ∩  { 𝑦  ∈  ( PSubSp ‘ 𝐾 )  ∣  𝑋  ⊆  𝑦 }  ⊆  ∩  { 𝑦  ∈  ( PSubSp ‘ 𝐾 )  ∣  𝑌  ⊆  𝑦 } )  | 
						
						
							| 9 | 
							
								
							 | 
							simp1 | 
							⊢ ( ( 𝐾  ∈  𝑉  ∧  𝑋  ⊆  𝑌  ∧  𝑌  ⊆  𝐴 )  →  𝐾  ∈  𝑉 )  | 
						
						
							| 10 | 
							
								
							 | 
							sstr | 
							⊢ ( ( 𝑋  ⊆  𝑌  ∧  𝑌  ⊆  𝐴 )  →  𝑋  ⊆  𝐴 )  | 
						
						
							| 11 | 
							
								10
							 | 
							3adant1 | 
							⊢ ( ( 𝐾  ∈  𝑉  ∧  𝑋  ⊆  𝑌  ∧  𝑌  ⊆  𝐴 )  →  𝑋  ⊆  𝐴 )  | 
						
						
							| 12 | 
							
								
							 | 
							eqid | 
							⊢ ( PSubSp ‘ 𝐾 )  =  ( PSubSp ‘ 𝐾 )  | 
						
						
							| 13 | 
							
								1 12 2
							 | 
							pclvalN | 
							⊢ ( ( 𝐾  ∈  𝑉  ∧  𝑋  ⊆  𝐴 )  →  ( 𝑈 ‘ 𝑋 )  =  ∩  { 𝑦  ∈  ( PSubSp ‘ 𝐾 )  ∣  𝑋  ⊆  𝑦 } )  | 
						
						
							| 14 | 
							
								9 11 13
							 | 
							syl2anc | 
							⊢ ( ( 𝐾  ∈  𝑉  ∧  𝑋  ⊆  𝑌  ∧  𝑌  ⊆  𝐴 )  →  ( 𝑈 ‘ 𝑋 )  =  ∩  { 𝑦  ∈  ( PSubSp ‘ 𝐾 )  ∣  𝑋  ⊆  𝑦 } )  | 
						
						
							| 15 | 
							
								1 12 2
							 | 
							pclvalN | 
							⊢ ( ( 𝐾  ∈  𝑉  ∧  𝑌  ⊆  𝐴 )  →  ( 𝑈 ‘ 𝑌 )  =  ∩  { 𝑦  ∈  ( PSubSp ‘ 𝐾 )  ∣  𝑌  ⊆  𝑦 } )  | 
						
						
							| 16 | 
							
								15
							 | 
							3adant2 | 
							⊢ ( ( 𝐾  ∈  𝑉  ∧  𝑋  ⊆  𝑌  ∧  𝑌  ⊆  𝐴 )  →  ( 𝑈 ‘ 𝑌 )  =  ∩  { 𝑦  ∈  ( PSubSp ‘ 𝐾 )  ∣  𝑌  ⊆  𝑦 } )  | 
						
						
							| 17 | 
							
								8 14 16
							 | 
							3sstr4d | 
							⊢ ( ( 𝐾  ∈  𝑉  ∧  𝑋  ⊆  𝑌  ∧  𝑌  ⊆  𝐴 )  →  ( 𝑈 ‘ 𝑋 )  ⊆  ( 𝑈 ‘ 𝑌 ) )  |