Database BASIC LINEAR ALGEBRA Vectors and free modules Free modules frlmrcl  
				
		 
		
			
		 
		Description:   If a free module is inhabited, this is sufficient to conclude that the
         ring expression defines a set.  (Contributed by Stefan O'Rear , 3-Feb-2015) 
		
			
				
					Ref 
					Expression 
				 
					
						Hypotheses 
						frlmval.f ⊢  𝐹   =  ( 𝑅   freeLMod  𝐼  )  
					
						frlmrcl.b ⊢  𝐵   =  ( Base ‘ 𝐹  )  
				
					Assertion 
					frlmrcl ⊢   ( 𝑋   ∈  𝐵   →  𝑅   ∈  V )  
			
		 
		
				Proof 
				
					
						Step 
						Hyp 
						Ref 
						Expression 
					 
						
							1 
								
							 
							frlmval.f ⊢  𝐹   =  ( 𝑅   freeLMod  𝐼  )  
						
							2 
								
							 
							frlmrcl.b ⊢  𝐵   =  ( Base ‘ 𝐹  )  
						
							3 
								
							 
							df-frlm ⊢   freeLMod   =  ( 𝑟   ∈  V ,  𝑖   ∈  V  ↦  ( 𝑟   ⊕m   ( 𝑖   ×  { ( ringLMod ‘ 𝑟  ) } ) ) )  
						
							4 
								3 
							 
							reldmmpo ⊢  Rel  dom   freeLMod   
						
							5 
								1  2  4 
							 
							strov2rcl ⊢  ( 𝑋   ∈  𝐵   →  𝑅   ∈  V )