| Step | Hyp | Ref | Expression | 
						
							| 1 |  | csbfrecsg |  |-  ( A e. V -> [_ A / x ]_ frecs ( R , D , ( F o. 2nd ) ) = frecs ( [_ A / x ]_ R , [_ A / x ]_ D , [_ A / x ]_ ( F o. 2nd ) ) ) | 
						
							| 2 |  | eqid |  |-  [_ A / x ]_ R = [_ A / x ]_ R | 
						
							| 3 |  | eqid |  |-  [_ A / x ]_ D = [_ A / x ]_ D | 
						
							| 4 |  | csbcog |  |-  ( A e. V -> [_ A / x ]_ ( F o. 2nd ) = ( [_ A / x ]_ F o. [_ A / x ]_ 2nd ) ) | 
						
							| 5 |  | csbconstg |  |-  ( A e. V -> [_ A / x ]_ 2nd = 2nd ) | 
						
							| 6 | 5 | coeq2d |  |-  ( A e. V -> ( [_ A / x ]_ F o. [_ A / x ]_ 2nd ) = ( [_ A / x ]_ F o. 2nd ) ) | 
						
							| 7 | 4 6 | eqtrd |  |-  ( A e. V -> [_ A / x ]_ ( F o. 2nd ) = ( [_ A / x ]_ F o. 2nd ) ) | 
						
							| 8 |  | frecseq123 |  |-  ( ( [_ A / x ]_ R = [_ A / x ]_ R /\ [_ A / x ]_ D = [_ A / x ]_ D /\ [_ A / x ]_ ( F o. 2nd ) = ( [_ A / x ]_ F o. 2nd ) ) -> frecs ( [_ A / x ]_ R , [_ A / x ]_ D , [_ A / x ]_ ( F o. 2nd ) ) = frecs ( [_ A / x ]_ R , [_ A / x ]_ D , ( [_ A / x ]_ F o. 2nd ) ) ) | 
						
							| 9 | 2 3 7 8 | mp3an12i |  |-  ( A e. V -> frecs ( [_ A / x ]_ R , [_ A / x ]_ D , [_ A / x ]_ ( F o. 2nd ) ) = frecs ( [_ A / x ]_ R , [_ A / x ]_ D , ( [_ A / x ]_ F o. 2nd ) ) ) | 
						
							| 10 | 1 9 | eqtrd |  |-  ( A e. V -> [_ A / x ]_ frecs ( R , D , ( F o. 2nd ) ) = frecs ( [_ A / x ]_ R , [_ A / x ]_ D , ( [_ A / x ]_ F o. 2nd ) ) ) | 
						
							| 11 |  | df-wrecs |  |-  wrecs ( R , D , F ) = frecs ( R , D , ( F o. 2nd ) ) | 
						
							| 12 | 11 | csbeq2i |  |-  [_ A / x ]_ wrecs ( R , D , F ) = [_ A / x ]_ frecs ( R , D , ( F o. 2nd ) ) | 
						
							| 13 |  | df-wrecs |  |-  wrecs ( [_ A / x ]_ R , [_ A / x ]_ D , [_ A / x ]_ F ) = frecs ( [_ A / x ]_ R , [_ A / x ]_ D , ( [_ A / x ]_ F o. 2nd ) ) | 
						
							| 14 | 10 12 13 | 3eqtr4g |  |-  ( A e. V -> [_ A / x ]_ wrecs ( R , D , F ) = wrecs ( [_ A / x ]_ R , [_ A / x ]_ D , [_ A / x ]_ F ) ) |