Metamath Proof Explorer
		
		
		
		Description:  A standard nonnegative integer is an extended nonnegative integer,
       deduction form.  (Contributed by AV, 10-Dec-2020)
		
			
				
					|  |  | Ref | Expression | 
					
						|  | Hypothesis | nn0xnn0d.1 |  | 
				
					|  | Assertion | nn0xnn0d |  | 
			
		
		
			
				Proof
				
					
						| Step | Hyp | Ref | Expression | 
						
							| 1 |  | nn0xnn0d.1 |  | 
						
							| 2 |  | nn0ssxnn0 |  | 
						
							| 3 | 2 1 | sselid |  |