Welcome to TeX.SE! You can add these marks with decorations.markings
. Since you want two of them, it is shorter to use the .list
key for that. Further, TikZ understands polar coordinates, and it also understands (0.5,{sqrt(3)/2})
, so there is no need to unbury your calculator. ;-)
\documentclass[tikz,border=3.14mm]{standalone}
\usetikzlibrary{decorations.markings}
\begin{document}
\begin{tikzpicture}[scale=5.5,equal mark/.style={postaction={decorate,
decoration={markings,mark=at position #1 with {\draw (-2pt,-4pt) -- (-2pt,4pt);
\draw (2pt,-4pt) -- (2pt,4pt);}}}}]
\coordinate[label=left:$A$] (A) at (0,0);
\coordinate[label=right:$B$] (B) at (1,0);
\coordinate[label=:$C$] (C) at (60:1);
\draw[equal mark/.list={1/6,1/2}] (A)--(B)--(C)--cycle;
\end{tikzpicture}
\end{document}

As you can see, this code starts with \documentclass
and ends with \end{document}
, and is compilable.
And you may simplify/shorten the code using a \foreach
loop.
\documentclass[tikz,border=3.14mm]{standalone}
\usetikzlibrary{decorations.markings}
\begin{document}
\begin{tikzpicture}[scale=5.5,equal mark/.style={postaction={decorate,
decoration={markings,mark=at position #1 with {\draw (-2pt,-4pt) -- (-2pt,4pt);
\draw (2pt,-4pt) -- (2pt,4pt);}}}}]
\foreach \X/\Y in {210/A,-30/B,90/C}
{\coordinate[label=\X:$\Y$] (\Y) at (\X:{1/sqrt(3)});}
\draw[equal mark/.list={1/6,1/2,5/6}] (A)--(B)--(C)--cycle;
\end{tikzpicture}
\end{document}
coordinate[label=:$C$] (C) at (60:1);
It also understandscoordinate[label=:$C$] (C) at (0.5,{sqrt(3)/2});
.