let G, H be non empty multMagma ; for x being Element of (product <*G,H*>) ex g being Element of G ex h being Element of H st x = <*g,h*>
let x be Element of (product <*G,H*>); ex g being Element of G ex h being Element of H st x = <*g,h*>
the carrier of (product <*G,H*>) = product (Carrier <*G,H*>)
by GROUP_7:def 2;
then consider g being Function such that
A1:
x = g
and
A2:
dom g = dom (Carrier <*G,H*>)
and
A3:
for y being object st y in dom (Carrier <*G,H*>) holds
g . y in (Carrier <*G,H*>) . y
by CARD_3:def 5;
A4:
ex R being 1-sorted st
( R = <*G,H*> . 2 & (Carrier <*G,H*>) . 2 = the carrier of R )
by Lm2, PRALG_1:def 15;
A5:
dom (Carrier <*G,H*>) = {1,2}
by PARTFUN1:def 2;
then reconsider g = g as FinSequence by A2, FINSEQ_1:2, FINSEQ_1:def 2;
g . 2 in (Carrier <*G,H*>) . 2
by A3, A5, Lm2;
then reconsider h1 = g . 2 as Element of H by A4;
A6:
ex R being 1-sorted st
( R = <*G,H*> . 1 & (Carrier <*G,H*>) . 1 = the carrier of R )
by Lm1, PRALG_1:def 15;
g . 1 in (Carrier <*G,H*>) . 1
by A3, A5, Lm1;
then reconsider g1 = g . 1 as Element of G by A6;
take
g1
; ex h being Element of H st x = <*g1,h*>
take
h1
; x = <*g1,h1*>
len g = 2
by A2, A5, FINSEQ_1:2, FINSEQ_1:def 3;
hence
x = <*g1,h1*>
by A1, FINSEQ_1:44; verum