# Isosceles triangle - equal side symbol

Other than manually placing a short line across the equal sides of a polygon, what should be the best practice to indicate that sides are equal length?

MWE:

\documentclass[12pt,table]{beamer}
\usepackage{tikz,pgfplots}

\begin{document}

\begin{frame}
\begin{figure}[!htbp]
\centering
\begin{tikzpicture}[scale=0.7]
\draw[] (0,0) -- (-4,-3) ;
\draw[] (0,0) -- (4,-3) ;
\draw[] (-4,-3) -- (4,-3);

\draw[thick,rotate around={34:(0,0)}] (-1.5,0.25) -- (-1.5,-0.25) ;
\draw[thick,rotate around={-34:(0,0)}] (1.5,0.25) -- (1.5,-0.25) ;
\end{tikzpicture}
\end{figure}
\end{frame}
\end{document}


this line you can draw with content of node:

\documentclass[12pt,table]{beamer}
\usepackage{pgfplots}
\usetikzlibrary{quotes}

\begin{document}

\begin{frame}
\begin{figure}
\centering
\begin{tikzpicture}[scale=0.7]
\draw   (0,0) -- node[sloped] {$|$} (-4,-3)
(0,0) -- node[sloped] {$|$} ( 4,-3)
(-4,-3) -- (4,-3);
\end{tikzpicture}
\end{figure}
\end{frame}
\end{document}


• Nice. Just a shorter code: \draw (-4,-3) -- node[sloped] {$|$} (0,0) -- node[sloped] {$|$} (4,-3) -- cycle; – Sigur Dec 1 '17 at 11:19

According to @Bernard's comment, one can declare the mark with tkz-euclide package (see page 77).

The following are two (slightly) different ways to represent isosceles triangles with provided coordinates and desired marks:

\documentclass[12pt,table]{beamer}
\usepackage{tikz,pgfplots}
\usepackage{tkz-euclide}

\begin{document}

\begin{frame}
\begin{figure}[!htbp]
\centering
\begin{tikzpicture}[scale=0.7]
\node (A) at (0,0){};
\node (B) at (-4,-3){};
\node (C) at (4,-3){};
\draw (0,0) -- (-4,-3);
\draw (0,0) -- (4,-3);
\draw (-4,-3) -- (4,-3);
\tkzDrawSegments(A,B C,B A,C)
\tkzMarkSegments[mark=|,color=red,size=6pt](C,A A,B)
\end{tikzpicture}

\bigskip

\begin{tikzpicture}[scale=0.7]
\tkzDefPoint(0,0){A}
\tkzDefPoint(4,3){B}
\tkzDefPoint(8,0){C}
\tkzDrawSegments(A,B C,B A,C)
\tkzMarkSegments[mark=|,color=red,size=6pt](C,B A,B)
\end{tikzpicture}
\end{figure}
\end{frame}

\end{document}


Dependeing on what you need, you can change character | by || or even |||, and also customize the color of the marks, as images above.

You can also use the following code (I took it from wikipedia here, and then modified it)

    \usepackage[pdftex,active,tightpage]{preview}
\usepackage{tikz}
\usetikzlibrary{positioning, calc}
% Begin tikz
\begin{tikzpicture}[scale=0.8]
\coordinate[label=left:$A$]  (A) at (-1,0);
\coordinate[label=right:$B$] (B) at (5,0);
\coordinate[label=above:$C$] (C) at (2,3.464);

% angle CAB
\begin{scope}[shift={(-1cm,0cm)}]
\draw[fill=green!30] (0,0) -- (0:0.6cm) arc (0:50:0.6cm);
\end{scope}
% angle CBA
\begin{scope}[shift={(5cm,0cm)}]
\draw[fill=green!30] (0,0) -- (-180:0.6cm) arc (180:130:0.6cm);
\end{scope}

% drawing triangle
\draw [line width=1.5pt] (A) --  (B)
(A) -- node[sloped] {$|$} (C)
(B) -- node[sloped] {$|$} (C);
\end{tikzpicture}


and you should get the following picture: