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\textit{Homework from Fuzzy Logic.
%Choose the basic or advanced level.
}

Exercise from classical logic.

\begin{exercise}
%\textbf{Basic level}
Prove that the axioms of classical logic
\begin{eqnarray*}
\lab(C1)&&A\IMPL(B\IMPL A)\cr
\lab(C2)&&(A\IMPL(B\IMPL C))\IMPL
              ((A\IMPL B)\IMPL(A\IMPL C))\cr
\lab(C3)&&(\NOT A\IMPL\NOT B)
        \IMPL(B\IMPL A)
\end{eqnarray*}
are tautologies.


%\bigskip
%\textbf{Advanced level}\\
\end{exercise}

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