let C, A be Ordinal; ( 1 in C & A <> {} & A is limit_ordinal implies for fi being Ordinal-Sequence st dom fi = A & ( for B being Ordinal st B in A holds
fi . B = exp C,B ) holds
exp C,A = sup fi )
assume that
A1:
1 in C
and
A2:
A <> {}
and
A3:
A is limit_ordinal
; for fi being Ordinal-Sequence st dom fi = A & ( for B being Ordinal st B in A holds
fi . B = exp C,B ) holds
exp C,A = sup fi
let fi be Ordinal-Sequence; ( dom fi = A & ( for B being Ordinal st B in A holds
fi . B = exp C,B ) implies exp C,A = sup fi )
assume that
A4:
dom fi = A
and
A5:
for B being Ordinal st B in A holds
fi . B = exp C,B
; exp C,A = sup fi
fi is increasing
by A1, A4, A5, Th25;
then
lim fi = sup fi
by A2, A3, A4, Th8;
hence
exp C,A = sup fi
by A2, A3, A4, A5, ORDINAL2:62; verum