let N be non empty with_non-empty_elements set ; for T being non empty stored-program IC-Ins-separated definite standard AMI-Struct of N
for k1, k2 being natural number holds
( il. T,k1 <= il. T,k2,T iff k1 <= k2 )
let T be non empty stored-program IC-Ins-separated definite standard AMI-Struct of N; for k1, k2 being natural number holds
( il. T,k1 <= il. T,k2,T iff k1 <= k2 )
let k1, k2 be natural number ; ( il. T,k1 <= il. T,k2,T iff k1 <= k2 )
A1:
( k1 is Element of NAT & k2 is Element of NAT )
by ORDINAL1:def 13;
consider f2 being Function of NAT ,NAT such that
A2:
( f2 is bijective & ( for m, n being Element of NAT holds
( m <= n iff f2 . m <= f2 . n,T ) ) )
and
A3:
il. T,k2 = f2 . k2
by Def12;
consider f1 being Function of NAT ,NAT such that
A4:
f1 is bijective
and
A5:
for m, n being Element of NAT holds
( m <= n iff f1 . m <= f1 . n,T )
and
A6:
il. T,k1 = f1 . k1
by Def12;
f1 = f2
by A4, A5, A2, Th17;
hence
( il. T,k1 <= il. T,k2,T iff k1 <= k2 )
by A1, A5, A6, A3; verum