Theorem showing that [ax-6] follows from the weaker version ax6v. (Even though this theorem depends on [ax-6], all references of [ax-6] are made via ax6v. An earlier version stated ax6v as a separate axiom, but having two axioms caused some confusion.)

This theorem should be referenced in place of [ax-6] so that all proofs can be traced back to ax6v. When possible, use the weaker ax6v rather than ax6 since the ax6v derivation is much shorter and requires fewer axioms. (Contributed by NM, 12-Nov-2013.) (Revised by NM, 25-Jul-2015.) (Proof shortened by Wolf Lammen, 4-Feb-2018.) Usage of this theorem is discouraged because it depends on [ax-13]. Use ax6v instead. (New usage is discouraged.)