|Description: Derivation of set.mm's
original ax-11o 2189 from ax-10 2188 and the shorter
ax-11 1757 that has replaced it.
An open problem is whether this theorem can be proved without relying on
ax-16 2192 or ax-17 1623 (given all of the original and new
versions of sp 1759
through ax-15 2191).
Another open problem is whether this theorem can be proved without
relying on ax12o 1976.
Theorem ax11 2203 shows the reverse derivation of ax-11 1757 from ax-11o 2189.
Normally, ax11o 2045 should be used rather than ax-11o 2189, except by
theorems specifically studying the latter's properties. (Contributed by