|Description: Derivation of set.mm's
original ax-11o 2093 from ax-10 2092 and the shorter
ax-11 1727 that has replaced it.
An open problem is whether this theorem can be proved without relying on
ax-16 2096 or ax-17 1606 (given all of the original and new
versions of sp 1728
through ax-15 2095).
Another open problem is whether this theorem can be proved without
relying on ax12o 1887.
Theorem ax11 2107 shows the reverse derivation of ax-11 1727 from ax-11o 2093.
Normally, ax11o 1947 should be used rather than ax-11o 2093, except by
theorems specifically studying the latter's properties. (Contributed by