set ccs = NonZero R;
set cR = the carrier of R;
reconsider ccs = NonZero R as non empty set ;
set mcs = the multF of R || ccs;
[:ccs,ccs:] c= [:the carrier of R,the carrier of R:]
then reconsider mcs = the multF of R || ccs as Function of [:ccs,ccs:],the carrier of R by FUNCT_2:38;
rng mcs c= ccs
proof
let y be
set ;
TARSKI:def 3 ( not y in rng mcs or y in ccs )
assume
y in rng mcs
;
y in ccs
then consider x being
set such that A1:
x in dom mcs
and A2:
y = mcs . x
by FUNCT_1:def 5;
A3:
dom mcs = [:ccs,ccs:]
by FUNCT_2:def 1;
then consider a,
b being
set such that A4:
a in ccs
and A5:
b in ccs
and A6:
x = [a,b]
by A1, ZFMISC_1:def 2;
reconsider a =
a,
b =
b as
Element of the
carrier of
R by A4, A5;
not
b in {(0. R)}
by A5, XBOOLE_0:def 5;
then A7:
b <> 0. R
by TARSKI:def 1;
not
a in {(0. R)}
by A4, XBOOLE_0:def 5;
then
a <> 0. R
by TARSKI:def 1;
then
a * b <> 0. R
by A7, VECTSP_2:47;
then A8:
not
a * b in {(0. R)}
by TARSKI:def 1;
mcs . x = a * b
by A1, A3, A6, FUNCT_1:72;
hence
y in ccs
by A2, A8, XBOOLE_0:def 5;
verum
end;
then reconsider mcs = mcs as BinOp of ccs by FUNCT_2:8;
reconsider cs = multMagma(# ccs,mcs #) as non empty multMagma ;
set ccs1 = the carrier of cs;
A11:
not 1_ R in {(0. R)}
by TARSKI:def 1;
A12:
cs is Group-like
cs is associative
hence
ex b1 being strict Group st
( the carrier of b1 = NonZero R & the multF of b1 = the multF of R || the carrier of b1 )
by A12; verum