| Step | Hyp | Ref | Expression | 
						
							| 1 |  | zre |  |-  ( N e. ZZ -> N e. RR ) | 
						
							| 2 |  | chpval |  |-  ( N e. RR -> ( psi ` N ) = sum_ n e. ( 1 ... ( |_ ` N ) ) ( Lam ` n ) ) | 
						
							| 3 | 1 2 | syl |  |-  ( N e. ZZ -> ( psi ` N ) = sum_ n e. ( 1 ... ( |_ ` N ) ) ( Lam ` n ) ) | 
						
							| 4 |  | flid |  |-  ( N e. ZZ -> ( |_ ` N ) = N ) | 
						
							| 5 | 4 | oveq2d |  |-  ( N e. ZZ -> ( 1 ... ( |_ ` N ) ) = ( 1 ... N ) ) | 
						
							| 6 | 5 | sumeq1d |  |-  ( N e. ZZ -> sum_ n e. ( 1 ... ( |_ ` N ) ) ( Lam ` n ) = sum_ n e. ( 1 ... N ) ( Lam ` n ) ) | 
						
							| 7 | 3 6 | eqtrd |  |-  ( N e. ZZ -> ( psi ` N ) = sum_ n e. ( 1 ... N ) ( Lam ` n ) ) |