Theorem 19.17

Theorem 19.17 of [Margaris] p. 90. (Contributed by NM, 12-Mar-1993.)

Hypothesis
19.17.1
\( \vdash \Finv x \, \psi \)
Conclusion
\( \vdash \forall x \, (\varphi \leftrightarrow \psi) \rightarrow (\forall x \, \varphi \leftrightarrow \psi) \)
Proof
l0
albi
\( \vdash \forall x \, (\varphi \leftrightarrow \psi) \rightarrow (\forall x \, \varphi \leftrightarrow \forall x \, \psi) \)
19.17.1
19.3 _
\( \vdash \forall x \, \psi \leftrightarrow \psi \)
bitrdi l0 _