\section{Protractor} Based on an idea by Yves Combe, the following macro allows you to draw a protractor. The operating principle is even simpler. Just name a half-line (a ray). The protractor will be placed on the origin $O$, the direction of the half-line is given by $A$. The angle is measured in the direct direction of the trigonometric circle. \subsection{The macro \tkzcname{tkzProtractor}} % (fold) \label{sub:the_macro_tkzcname_tkzprotractor} % subsection the_macro_tkzcname_tkzprotractor (end) \begin{NewMacroBox}{tkzProtractor}{\oarg{local options}\parg{$O,A$}}% \begin{tabular}{lll}% options & default & definition \\ \midrule \TOline{lw} {0.4 pt} {line thickness} \TOline{scale} {1} {ratio: adjusts the size of the protractor} \TOline{return} {false} {trigonometric circle indirect} \end{tabular} \end{NewMacroBox} \subsubsection{The circular protractor} Measuring in the forward direction \begin{tkzexample}[latex=7cm,small] \begin{tikzpicture}[scale=.5] \tkzDefPoint(2,0){A}\tkzDefPoint(0,0){O} \tkzDefShiftPoint[A](31:5){B} \tkzDefShiftPoint[A](158:5){C} \tkzDrawPoints(A,B,C) \tkzDrawSegments[color = red, line width = 1pt](A,B A,C) \tkzProtractor[scale = 1](A,B) \end{tikzpicture} \end{tkzexample} \subsubsection{The circular protractor, transparent and returned} \begin{tkzexample}[latex=7cm,small] \begin{tikzpicture}[scale=.5] \tkzDefPoint(2,3){A} \tkzDefShiftPoint[A](31:5){B} \tkzDefShiftPoint[A](158:5){C} \tkzDrawSegments[color=red,line width=1pt](A,B A,C) \tkzProtractor[return](A,C) \end{tikzpicture} \end{tkzexample} \endinput