take 1 ; :: according to AMISTD_2:def 12 :: thesis: ( 1 in dom (AddressPart (goto i1,R)) & (product" (AddressParts (InsCode (goto i1,R)))) . 1 = NAT )
dom (AddressPart (goto i1,R)) = dom <*i1*> by MCART_1:def 2
.= {1} by FINSEQ_1:4, FINSEQ_1:def 8 ;
hence 1 in dom (AddressPart (goto i1,R)) by TARSKI:def 1; :: thesis: (product" (AddressParts (InsCode (goto i1,R)))) . 1 = NAT
thus (product" (AddressParts (InsCode (goto i1,R)))) . 1 = NAT by Th50; :: thesis: verum