Theorem anbi12ci

Variant of anbi12i with commutation. (Contributed by Jonathan Ben-Naim, 3-Jun-2011.)

Hypotheses
anbi12.1
\( \vdash \varphi \leftrightarrow \psi \)
anbi12.2
\( \vdash \chi \leftrightarrow \theta \)
Conclusion
\( \vdash \varphi \wedge \chi \leftrightarrow \theta \wedge \psi \)
Proof
l0
anbi12.1
anbi12.2
anbi12i l0 _
biancomi _