|Description: Derivation of set.mm's
original ax-11o 2085 from ax-10 2084 and the shorter
ax-11 1718 that has replaced it.
An open problem is whether this theorem can be proved without relying on
ax-16 2088 or ax-17 1605 (given all of the original and new
versions of sp 1719
through ax-15 2087).
Another open problem is whether this theorem can be proved without
relying on ax12o 1879.
Theorem ax11 2098 shows the reverse derivation of ax-11 1718 from ax-11o 2085.
Normally, ax11o 1939 should be used rather than ax-11o 2085, except by
theorems specifically studying the latter's properties. (Contributed by