| Step | Hyp | Ref | Expression | 
						
							| 1 |  | qusaddf.u | ⊢ ( 𝜑  →  𝑈  =  ( 𝑅  /s   ∼  ) ) | 
						
							| 2 |  | qusaddf.v | ⊢ ( 𝜑  →  𝑉  =  ( Base ‘ 𝑅 ) ) | 
						
							| 3 |  | qusaddf.r | ⊢ ( 𝜑  →   ∼   Er  𝑉 ) | 
						
							| 4 |  | qusaddf.z | ⊢ ( 𝜑  →  𝑅  ∈  𝑍 ) | 
						
							| 5 |  | qusaddf.e | ⊢ ( 𝜑  →  ( ( 𝑎  ∼  𝑝  ∧  𝑏  ∼  𝑞 )  →  ( 𝑎  ·  𝑏 )  ∼  ( 𝑝  ·  𝑞 ) ) ) | 
						
							| 6 |  | qusaddf.c | ⊢ ( ( 𝜑  ∧  ( 𝑝  ∈  𝑉  ∧  𝑞  ∈  𝑉 ) )  →  ( 𝑝  ·  𝑞 )  ∈  𝑉 ) | 
						
							| 7 |  | qusaddflem.f | ⊢ 𝐹  =  ( 𝑥  ∈  𝑉  ↦  [ 𝑥 ]  ∼  ) | 
						
							| 8 |  | qusaddflem.g | ⊢ ( 𝜑  →   ∙   =  ∪  𝑝  ∈  𝑉 ∪  𝑞  ∈  𝑉 { 〈 〈 ( 𝐹 ‘ 𝑝 ) ,  ( 𝐹 ‘ 𝑞 ) 〉 ,  ( 𝐹 ‘ ( 𝑝  ·  𝑞 ) ) 〉 } ) | 
						
							| 9 |  | fvex | ⊢ ( Base ‘ 𝑅 )  ∈  V | 
						
							| 10 | 2 9 | eqeltrdi | ⊢ ( 𝜑  →  𝑉  ∈  V ) | 
						
							| 11 |  | erex | ⊢ (  ∼   Er  𝑉  →  ( 𝑉  ∈  V  →   ∼   ∈  V ) ) | 
						
							| 12 | 3 10 11 | sylc | ⊢ ( 𝜑  →   ∼   ∈  V ) | 
						
							| 13 | 1 2 7 12 4 | quslem | ⊢ ( 𝜑  →  𝐹 : 𝑉 –onto→ ( 𝑉  /   ∼  ) ) | 
						
							| 14 | 3 10 7 6 5 | ercpbl | ⊢ ( ( 𝜑  ∧  ( 𝑎  ∈  𝑉  ∧  𝑏  ∈  𝑉 )  ∧  ( 𝑝  ∈  𝑉  ∧  𝑞  ∈  𝑉 ) )  →  ( ( ( 𝐹 ‘ 𝑎 )  =  ( 𝐹 ‘ 𝑝 )  ∧  ( 𝐹 ‘ 𝑏 )  =  ( 𝐹 ‘ 𝑞 ) )  →  ( 𝐹 ‘ ( 𝑎  ·  𝑏 ) )  =  ( 𝐹 ‘ ( 𝑝  ·  𝑞 ) ) ) ) | 
						
							| 15 | 13 14 8 | imasaddvallem | ⊢ ( ( 𝜑  ∧  𝑋  ∈  𝑉  ∧  𝑌  ∈  𝑉 )  →  ( ( 𝐹 ‘ 𝑋 )  ∙  ( 𝐹 ‘ 𝑌 ) )  =  ( 𝐹 ‘ ( 𝑋  ·  𝑌 ) ) ) | 
						
							| 16 | 3 | 3ad2ant1 | ⊢ ( ( 𝜑  ∧  𝑋  ∈  𝑉  ∧  𝑌  ∈  𝑉 )  →   ∼   Er  𝑉 ) | 
						
							| 17 | 10 | 3ad2ant1 | ⊢ ( ( 𝜑  ∧  𝑋  ∈  𝑉  ∧  𝑌  ∈  𝑉 )  →  𝑉  ∈  V ) | 
						
							| 18 | 16 17 7 | divsfval | ⊢ ( ( 𝜑  ∧  𝑋  ∈  𝑉  ∧  𝑌  ∈  𝑉 )  →  ( 𝐹 ‘ 𝑋 )  =  [ 𝑋 ]  ∼  ) | 
						
							| 19 | 16 17 7 | divsfval | ⊢ ( ( 𝜑  ∧  𝑋  ∈  𝑉  ∧  𝑌  ∈  𝑉 )  →  ( 𝐹 ‘ 𝑌 )  =  [ 𝑌 ]  ∼  ) | 
						
							| 20 | 18 19 | oveq12d | ⊢ ( ( 𝜑  ∧  𝑋  ∈  𝑉  ∧  𝑌  ∈  𝑉 )  →  ( ( 𝐹 ‘ 𝑋 )  ∙  ( 𝐹 ‘ 𝑌 ) )  =  ( [ 𝑋 ]  ∼   ∙  [ 𝑌 ]  ∼  ) ) | 
						
							| 21 | 16 17 7 | divsfval | ⊢ ( ( 𝜑  ∧  𝑋  ∈  𝑉  ∧  𝑌  ∈  𝑉 )  →  ( 𝐹 ‘ ( 𝑋  ·  𝑌 ) )  =  [ ( 𝑋  ·  𝑌 ) ]  ∼  ) | 
						
							| 22 | 15 20 21 | 3eqtr3d | ⊢ ( ( 𝜑  ∧  𝑋  ∈  𝑉  ∧  𝑌  ∈  𝑉 )  →  ( [ 𝑋 ]  ∼   ∙  [ 𝑌 ]  ∼  )  =  [ ( 𝑋  ·  𝑌 ) ]  ∼  ) |