2019-05-27 扇型を描く <script type="text/tikz"> \begin{tikzpicture} \draw [-stealth](-2,0)--(2,0); \draw [-stealth](0,-2)--(0,2); \filldraw [fill=blue, opacity=.5, draw=red](0,0)--(1,0)--(1,0)arc(0:120:1)--cycle; \end{tikzpicture} </script>