Theorem aecom

Commutation law for identical variable specifiers. Both sides of the biconditional are true when \( x \) and \( y \) are substituted with the same variable. Usage of this theorem is discouraged because it depends on [ax-13]. (Contributed by NM, 10-May-1993.) Change to a biconditional. (Revised by BJ, 26-Sep-2019.) (New usage is discouraged.)

Conclusion
\( \vdash \forall x \, x = y \leftrightarrow \forall y \, y = x \)
Proof
l0
axc11n
axc11n
impbii l0 _