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LaTeX で増減表に用いる曲った矢印

1. bendarrow.sty

真直な矢印は LaTeX 標準の $\nearrow$ と $\searrow$ を使う.

曲り矢印の定義:

%% 曲り矢印 10pt x 10pt 相当
\def\lbarrow{{\begin{picture}(10,10) 
      \put(10,10){\oval(20,20)[lb]}\put(10,0){\vector(1,0){2}}
    \end{picture}}}
\def\ltarrow{{\begin{picture}(10,10) 
      \put(10,0){\oval(20,20)[lt]}\put(10,10){\vector(1,0){2}}
    \end{picture}}}
\def\rbarrow{{\begin{picture}(10,10) 
      \put(0,10){\oval(20,20)[rb]}\put(10,10){\vector(0,1){2}}
    \end{picture}}}
\def\rtarrow{{\begin{picture}(10,10) 
      \put(0,0){\oval(20,20)[rt]}\put(10,0){\vector(0,-1){2}}
    \end{picture}}}

使用例:

\documentclass{article}

\usepackage{bendarrow}

\begin{document}
増減表\\
\begin{tabular}{c||c|c|c|c|c|c|c}
  $x$ &   & 1&   & 2 & & 3 & \\ \hline
  $y'$ & $+$ &  0  & $-$ & $-$ & $-$ & 0 & $+$  \\
  $y^{\prime\prime}$ & $-$ & $-$ & $-$ & 0 & $+$ & $+$ & $+$ \\ \hline
  $y$  & \ltarrow & $\mbox{極大}\atop 3$  & \rtarrow & $\mbox{変曲点}\atop 2 $ & \lbarrow & $\mbox{極小}\atop 1$ & \rbarrow
\end{tabular}
\\
\ltarrow \rtarrow \\
\lbarrow \rbarrow \\

\end{document}

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