| Step | Hyp | Ref | Expression | 
						
							| 1 |  | dvh3dim.h | ⊢ 𝐻  =  ( LHyp ‘ 𝐾 ) | 
						
							| 2 |  | dvh3dim.u | ⊢ 𝑈  =  ( ( DVecH ‘ 𝐾 ) ‘ 𝑊 ) | 
						
							| 3 |  | dvh3dim.v | ⊢ 𝑉  =  ( Base ‘ 𝑈 ) | 
						
							| 4 |  | dvh3dim.n | ⊢ 𝑁  =  ( LSpan ‘ 𝑈 ) | 
						
							| 5 |  | dvh3dim.k | ⊢ ( 𝜑  →  ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 ) ) | 
						
							| 6 |  | dvh3dim.x | ⊢ ( 𝜑  →  𝑋  ∈  𝑉 ) | 
						
							| 7 |  | dvhdim.y | ⊢ ( 𝜑  →  𝑌  ∈  𝑉 ) | 
						
							| 8 |  | dvhdim.o | ⊢  0   =  ( 0g ‘ 𝑈 ) | 
						
							| 9 |  | dvhdim.x | ⊢ ( 𝜑  →  𝑋  ≠   0  ) | 
						
							| 10 |  | dvhdimlem.y | ⊢ ( 𝜑  →  𝑌  ≠   0  ) | 
						
							| 11 | 1 2 3 4 5 6 7 7 8 9 10 10 | dvh4dimlem | ⊢ ( 𝜑  →  ∃ 𝑧  ∈  𝑉 ¬  𝑧  ∈  ( 𝑁 ‘ { 𝑋 ,  𝑌 ,  𝑌 } ) ) | 
						
							| 12 | 1 2 5 | dvhlmod | ⊢ ( 𝜑  →  𝑈  ∈  LMod ) | 
						
							| 13 |  | df-tp | ⊢ { 𝑋 ,  𝑌 ,  𝑌 }  =  ( { 𝑋 ,  𝑌 }  ∪  { 𝑌 } ) | 
						
							| 14 |  | prssi | ⊢ ( ( 𝑋  ∈  𝑉  ∧  𝑌  ∈  𝑉 )  →  { 𝑋 ,  𝑌 }  ⊆  𝑉 ) | 
						
							| 15 | 6 7 14 | syl2anc | ⊢ ( 𝜑  →  { 𝑋 ,  𝑌 }  ⊆  𝑉 ) | 
						
							| 16 | 7 | snssd | ⊢ ( 𝜑  →  { 𝑌 }  ⊆  𝑉 ) | 
						
							| 17 | 15 16 | unssd | ⊢ ( 𝜑  →  ( { 𝑋 ,  𝑌 }  ∪  { 𝑌 } )  ⊆  𝑉 ) | 
						
							| 18 | 13 17 | eqsstrid | ⊢ ( 𝜑  →  { 𝑋 ,  𝑌 ,  𝑌 }  ⊆  𝑉 ) | 
						
							| 19 |  | ssun1 | ⊢ { 𝑋 ,  𝑌 }  ⊆  ( { 𝑋 ,  𝑌 }  ∪  { 𝑌 } ) | 
						
							| 20 | 19 13 | sseqtrri | ⊢ { 𝑋 ,  𝑌 }  ⊆  { 𝑋 ,  𝑌 ,  𝑌 } | 
						
							| 21 | 20 | a1i | ⊢ ( 𝜑  →  { 𝑋 ,  𝑌 }  ⊆  { 𝑋 ,  𝑌 ,  𝑌 } ) | 
						
							| 22 | 3 4 | lspss | ⊢ ( ( 𝑈  ∈  LMod  ∧  { 𝑋 ,  𝑌 ,  𝑌 }  ⊆  𝑉  ∧  { 𝑋 ,  𝑌 }  ⊆  { 𝑋 ,  𝑌 ,  𝑌 } )  →  ( 𝑁 ‘ { 𝑋 ,  𝑌 } )  ⊆  ( 𝑁 ‘ { 𝑋 ,  𝑌 ,  𝑌 } ) ) | 
						
							| 23 | 12 18 21 22 | syl3anc | ⊢ ( 𝜑  →  ( 𝑁 ‘ { 𝑋 ,  𝑌 } )  ⊆  ( 𝑁 ‘ { 𝑋 ,  𝑌 ,  𝑌 } ) ) | 
						
							| 24 | 23 | ssneld | ⊢ ( 𝜑  →  ( ¬  𝑧  ∈  ( 𝑁 ‘ { 𝑋 ,  𝑌 ,  𝑌 } )  →  ¬  𝑧  ∈  ( 𝑁 ‘ { 𝑋 ,  𝑌 } ) ) ) | 
						
							| 25 | 24 | reximdv | ⊢ ( 𝜑  →  ( ∃ 𝑧  ∈  𝑉 ¬  𝑧  ∈  ( 𝑁 ‘ { 𝑋 ,  𝑌 ,  𝑌 } )  →  ∃ 𝑧  ∈  𝑉 ¬  𝑧  ∈  ( 𝑁 ‘ { 𝑋 ,  𝑌 } ) ) ) | 
						
							| 26 | 11 25 | mpd | ⊢ ( 𝜑  →  ∃ 𝑧  ∈  𝑉 ¬  𝑧  ∈  ( 𝑁 ‘ { 𝑋 ,  𝑌 } ) ) |