¬(P∨Q)⇒¬P∧¬Q

証明

https://scrapbox.io/files/68a7fb9d849b0d80a3867cee.svg

code:proof.tikz(tex)

\usepackage{fitch}

\usepackage{amsmath}

\begin{document}

$\Large\begin{nd}

\hypo {h} {\lnot(P\lor Q)}

\open

\hypo {p} {P}

\have {pq} {P\lor Q} \oi{p}

\have {b} {\bot} \ne{h,pq}

\close

\have {np} {\lnot P} \ii{p-b}

\open

\hypo {q} {Q}

\have {pq} {P\lor Q} \oi{q}

\have {b} {\bot} \ne{h,pq}

\close

\have {nq} {\lnot Q} \ii{q-b}

\have {pq} {\lnot P\land\lnot Q} \ai{np,nq}

\end{nd}$

\end{document}