A direct proof of nic-mp. (Contributed by NM, 30-Dec-2008.)
(Proof modification is discouraged.) (New usage is discouraged.)
\( \vdash \varphi \barwedge (\chi \barwedge \psi) \leftrightarrow \neg (\varphi \wedge (\chi \barwedge \psi)) \)
\( \vdash \varphi \wedge (\chi \barwedge \psi) \leftrightarrow \varphi \wedge \neg (\chi \wedge \psi) \)
\( \vdash \varphi \barwedge (\chi \barwedge \psi) \leftrightarrow \neg (\varphi \wedge \neg (\chi \wedge \psi)) \)
\( \vdash \varphi \rightarrow \chi \wedge \psi \leftrightarrow \neg (\varphi \wedge \neg (\chi \wedge \psi)) \)