Planar Curves with TikZ

1. Hat Vector: \[ \underline{\widehat{a}}= \begin{pmatrix} -a_y\\a_x \end{pmatrix} \]
   
2. $\LaTeX/TikZ$:

   TiKZ Listing: Hat.tikz.tex. PDF   PNG   SVG   ZIP*   %%%%\documentclass{standalone} \input{../../../PreAmble.tikz} %%%%\begin{document} %%%%\begin{tikzpicture} \tikzmath{\ax=4;} \tikzmath{\ay=2;} \coordinate (O) at (0,0); \coordinate (a) at (\ax,\ay); \coordinate (at) at (-\ay,\ax); \draw[-latex] (O) -- (a); \draw[-latex] (O) -- (at); \node at ($1.1*(a)$) {$\underline{a}$}; \node at ($1.1*(at)$) {$\underline{\widehat{a}}$}; \tkzMarkRightAngle(a,O,at); \tkzMarkAngle[size=2,arrows=-latex](a,O,at); \tkzLabelAngle[pos=2.3](a,O,at) {$+$}; %%%%\end{tikzpicture} %%%%\end{document}