| Step | Hyp | Ref | Expression | 
						
							| 1 |  | doch11.h | ⊢ 𝐻  =  ( LHyp ‘ 𝐾 ) | 
						
							| 2 |  | doch11.i | ⊢ 𝐼  =  ( ( DIsoH ‘ 𝐾 ) ‘ 𝑊 ) | 
						
							| 3 |  | doch11.o | ⊢  ⊥   =  ( ( ocH ‘ 𝐾 ) ‘ 𝑊 ) | 
						
							| 4 |  | doch11.k | ⊢ ( 𝜑  →  ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 ) ) | 
						
							| 5 |  | doch11.x | ⊢ ( 𝜑  →  𝑋  ∈  ran  𝐼 ) | 
						
							| 6 |  | doch11.y | ⊢ ( 𝜑  →  𝑌  ∈  ran  𝐼 ) | 
						
							| 7 |  | eqid | ⊢ ( ( DVecH ‘ 𝐾 ) ‘ 𝑊 )  =  ( ( DVecH ‘ 𝐾 ) ‘ 𝑊 ) | 
						
							| 8 |  | eqid | ⊢ ( LSubSp ‘ ( ( DVecH ‘ 𝐾 ) ‘ 𝑊 ) )  =  ( LSubSp ‘ ( ( DVecH ‘ 𝐾 ) ‘ 𝑊 ) ) | 
						
							| 9 | 1 7 2 8 | dihrnlss | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  𝑌  ∈  ran  𝐼 )  →  𝑌  ∈  ( LSubSp ‘ ( ( DVecH ‘ 𝐾 ) ‘ 𝑊 ) ) ) | 
						
							| 10 | 4 6 9 | syl2anc | ⊢ ( 𝜑  →  𝑌  ∈  ( LSubSp ‘ ( ( DVecH ‘ 𝐾 ) ‘ 𝑊 ) ) ) | 
						
							| 11 |  | eqid | ⊢ ( Base ‘ ( ( DVecH ‘ 𝐾 ) ‘ 𝑊 ) )  =  ( Base ‘ ( ( DVecH ‘ 𝐾 ) ‘ 𝑊 ) ) | 
						
							| 12 | 11 8 | lssss | ⊢ ( 𝑌  ∈  ( LSubSp ‘ ( ( DVecH ‘ 𝐾 ) ‘ 𝑊 ) )  →  𝑌  ⊆  ( Base ‘ ( ( DVecH ‘ 𝐾 ) ‘ 𝑊 ) ) ) | 
						
							| 13 | 10 12 | syl | ⊢ ( 𝜑  →  𝑌  ⊆  ( Base ‘ ( ( DVecH ‘ 𝐾 ) ‘ 𝑊 ) ) ) | 
						
							| 14 | 1 2 7 11 3 | dochcl | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  𝑌  ⊆  ( Base ‘ ( ( DVecH ‘ 𝐾 ) ‘ 𝑊 ) ) )  →  (  ⊥  ‘ 𝑌 )  ∈  ran  𝐼 ) | 
						
							| 15 | 4 13 14 | syl2anc | ⊢ ( 𝜑  →  (  ⊥  ‘ 𝑌 )  ∈  ran  𝐼 ) | 
						
							| 16 | 1 2 3 4 5 15 | dochord | ⊢ ( 𝜑  →  ( 𝑋  ⊆  (  ⊥  ‘ 𝑌 )  ↔  (  ⊥  ‘ (  ⊥  ‘ 𝑌 ) )  ⊆  (  ⊥  ‘ 𝑋 ) ) ) | 
						
							| 17 | 1 2 3 | dochoc | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  𝑌  ∈  ran  𝐼 )  →  (  ⊥  ‘ (  ⊥  ‘ 𝑌 ) )  =  𝑌 ) | 
						
							| 18 | 4 6 17 | syl2anc | ⊢ ( 𝜑  →  (  ⊥  ‘ (  ⊥  ‘ 𝑌 ) )  =  𝑌 ) | 
						
							| 19 | 18 | sseq1d | ⊢ ( 𝜑  →  ( (  ⊥  ‘ (  ⊥  ‘ 𝑌 ) )  ⊆  (  ⊥  ‘ 𝑋 )  ↔  𝑌  ⊆  (  ⊥  ‘ 𝑋 ) ) ) | 
						
							| 20 | 16 19 | bitrd | ⊢ ( 𝜑  →  ( 𝑋  ⊆  (  ⊥  ‘ 𝑌 )  ↔  𝑌  ⊆  (  ⊥  ‘ 𝑋 ) ) ) |