Theorem exbidv

Formula-building rule for existential quantifier (deduction form). See also exbidh and exbid. (Contributed by NM, 26-May-1993.)

Hypothesis
albidv.1
\( \vdash \varphi \rightarrow (\psi \leftrightarrow \chi) \)
Conclusion
\( \vdash \varphi \rightarrow (\exists x \, \psi \leftrightarrow \exists x \, \chi) \)
Proof
l0
ax-5
albidv.1
exbidh l0 _