take {{}} ; :: according to COMPOS_0:def 1 :: thesis: {[1,{},{}]} c= [:NAT,(NAT *),({{}} *):]
A3: {{}} c= {{}} * by ZFMISC_1:31, FINSEQ_1:49;
A4: {{}} c= NAT * by ZFMISC_1:31, FINSEQ_1:49;
{[1,{},{}]} = [:{1},{{}},{{}}:] by MCART_1:35;
hence {[1,{},{}]} c= [:NAT,(NAT *),({{}} *):] by A3, A4, MCART_1:73; :: thesis: verum