| Step | Hyp | Ref | Expression | 
						
							| 1 |  | erngset.h-r | ⊢ 𝐻  =  ( LHyp ‘ 𝐾 ) | 
						
							| 2 |  | erngset.t-r | ⊢ 𝑇  =  ( ( LTrn ‘ 𝐾 ) ‘ 𝑊 ) | 
						
							| 3 |  | erngset.e-r | ⊢ 𝐸  =  ( ( TEndo ‘ 𝐾 ) ‘ 𝑊 ) | 
						
							| 4 |  | erngset.d-r | ⊢ 𝐷  =  ( ( EDRingR ‘ 𝐾 ) ‘ 𝑊 ) | 
						
							| 5 |  | erng.p-r | ⊢  +   =  ( +g ‘ 𝐷 ) | 
						
							| 6 | 1 2 3 4 5 | erngplus-rN | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  ( 𝑈  ∈  𝐸  ∧  𝑉  ∈  𝐸 ) )  →  ( 𝑈  +  𝑉 )  =  ( 𝑓  ∈  𝑇  ↦  ( ( 𝑈 ‘ 𝑓 )  ∘  ( 𝑉 ‘ 𝑓 ) ) ) ) | 
						
							| 7 | 6 | 3adantr3 | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  ( 𝑈  ∈  𝐸  ∧  𝑉  ∈  𝐸  ∧  𝐹  ∈  𝑇 ) )  →  ( 𝑈  +  𝑉 )  =  ( 𝑓  ∈  𝑇  ↦  ( ( 𝑈 ‘ 𝑓 )  ∘  ( 𝑉 ‘ 𝑓 ) ) ) ) | 
						
							| 8 |  | fveq2 | ⊢ ( 𝑓  =  𝐹  →  ( 𝑈 ‘ 𝑓 )  =  ( 𝑈 ‘ 𝐹 ) ) | 
						
							| 9 |  | fveq2 | ⊢ ( 𝑓  =  𝐹  →  ( 𝑉 ‘ 𝑓 )  =  ( 𝑉 ‘ 𝐹 ) ) | 
						
							| 10 | 8 9 | coeq12d | ⊢ ( 𝑓  =  𝐹  →  ( ( 𝑈 ‘ 𝑓 )  ∘  ( 𝑉 ‘ 𝑓 ) )  =  ( ( 𝑈 ‘ 𝐹 )  ∘  ( 𝑉 ‘ 𝐹 ) ) ) | 
						
							| 11 | 10 | adantl | ⊢ ( ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  ( 𝑈  ∈  𝐸  ∧  𝑉  ∈  𝐸  ∧  𝐹  ∈  𝑇 ) )  ∧  𝑓  =  𝐹 )  →  ( ( 𝑈 ‘ 𝑓 )  ∘  ( 𝑉 ‘ 𝑓 ) )  =  ( ( 𝑈 ‘ 𝐹 )  ∘  ( 𝑉 ‘ 𝐹 ) ) ) | 
						
							| 12 |  | simpr3 | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  ( 𝑈  ∈  𝐸  ∧  𝑉  ∈  𝐸  ∧  𝐹  ∈  𝑇 ) )  →  𝐹  ∈  𝑇 ) | 
						
							| 13 |  | fvex | ⊢ ( 𝑈 ‘ 𝐹 )  ∈  V | 
						
							| 14 |  | fvex | ⊢ ( 𝑉 ‘ 𝐹 )  ∈  V | 
						
							| 15 | 13 14 | coex | ⊢ ( ( 𝑈 ‘ 𝐹 )  ∘  ( 𝑉 ‘ 𝐹 ) )  ∈  V | 
						
							| 16 | 15 | a1i | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  ( 𝑈  ∈  𝐸  ∧  𝑉  ∈  𝐸  ∧  𝐹  ∈  𝑇 ) )  →  ( ( 𝑈 ‘ 𝐹 )  ∘  ( 𝑉 ‘ 𝐹 ) )  ∈  V ) | 
						
							| 17 | 7 11 12 16 | fvmptd | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  ( 𝑈  ∈  𝐸  ∧  𝑉  ∈  𝐸  ∧  𝐹  ∈  𝑇 ) )  →  ( ( 𝑈  +  𝑉 ) ‘ 𝐹 )  =  ( ( 𝑈 ‘ 𝐹 )  ∘  ( 𝑉 ‘ 𝐹 ) ) ) |