|Description: Derivation of set.mm's
original ax-11o 2141 from ax-10 2140 and the shorter
ax-11 1746 that has replaced it.
An open problem is whether this theorem can be proved without relying on
ax-16 2144 or ax-17 1616 (given all of the original and new
versions of sp 1747
through ax-15 2143).
Another open problem is whether this theorem can be proved without
relying on ax12o 1934.
Theorem ax11 2155 shows the reverse derivation of ax-11 1746 from ax-11o 2141.
Normally, ax11o 1994 should be used rather than ax-11o 2141, except by
theorems specifically studying the latter's properties. (Contributed by