Triangle with text

Question

Can someone help me draw a equilateral triangle with numbers 1, 2, 3 at each interior angle of it? Also I need to equate a letter with that triangle; namely F = graph. Thanks in advance.

Answer 1

Without any fancy techniques:

\documentclass[tikz,border=5mm]{standalone}
\usetikzlibrary{positioning}

\begin{document}
\begin{tikzpicture}
\coordinate (a) at (0,0);
\coordinate (b) at (2cm,0);
\coordinate (c) at (60:2cm);
\node[above left = 0.65cm and 0cm of a] {$F=$};   %% change distances suitably
%
\draw (a) -- (b) -- (c) -- cycle;
\path[clip] (a) -- (b) -- (c) -- cycle;
\node[circle,draw,minimum size=0.4cm] at (a) {};
\node[font=\tiny,inner sep=0pt] at (30:0.3cm) {$1$};
\node[circle,draw,minimum size=0.4cm] at (b) (circa) {}
node[font=\tiny,inner sep=0pt,above left = 0.1cm and 0.2cm of b]  {$2$};
\node[circle,draw,minimum size=0.4cm] at (c) (circa) {} 
node[font=\tiny,inner sep=0pt,below = 0.25cm of c] {$3$};
\end{tikzpicture}

\end{document}

Adopting the code from Torbjorn's answer:

\documentclass[border=5mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{shapes.geometric,positioning}

\tikzset{
    buffer/.style={
        draw,
        name=s,
        shape border rotate=0,
        regular polygon,
        regular polygon sides=3,        
        node distance=2cm,
        minimum height=4em
    }
}

\begin{document}
\begin{tikzpicture}
\node[buffer,label={left:$F=\,$}]{};
\clip (s.corner 1) -- (s.corner 2) -- (s.corner 3) --cycle;
\draw (s.corner 1) circle (0.2cm) node[font=\tiny,inner sep=0pt,below = 0.25cm of s.corner 1] {$3$};
\draw (s.corner 2) circle (0.2cm) node[font=\tiny,inner sep=0pt,,above right = 0.1cm and 0.2cm of s.corner 2] {$1$};
\draw (s.corner 3) circle (0.2cm) node[font=\tiny,inner sep=0pt,,above left = 0.1cm and 0.2cm of s.corner 3] {$2$};
\end{tikzpicture}
\end{document}

Answer 2

Perhaps...

\documentclass[border=0.125cm]{standalone}
\usepackage{tikz}
\begin{document}    
F=\tikz[scale=.625,baseline=0pt]{
  \clip[preaction=draw] (-30:1) -- (90:1) -- (210:1) -- cycle;
  \draw\foreach \i [count=\j] in {90,210,-30}{ 
    (\i:1) circle [radius=.25] (\i:.875) node [anchor=\i,font=\tiny] {\j}};}
\end{document}

or

\documentclass[border=0.125cm]{standalone}
\usepackage{tikz}
\begin{document}
F=\tikz[scale=.625, baseline=0pt, inner sep=1pt]
    \draw  (-30:1) -- (90:1) -- (210:1) -- cycle
      \foreach \i [count=\j] in {90,210,-30}{ [shift={(\i:1)}, rotate=\i+150] 
        (.25,0) arc (0:60:.25) node [midway, anchor=\i, font=\tiny] {\j}};
\end{document}

Which produces (roughly) the same image as above.

Answer 3

With PSTricks just for fun.

\documentclass[pstricks,border=12pt,12pt]{standalone}
\usepackage{pst-eucl}

\begin{document}
\multido{\n=.0+.1}{11}{%
\begin{pspicture}[LabelSep=.7,PointSymbol=none,PointName=none,CurveType=polygon](-.8,0)(3,3)
    \pstGeonode{A}(3,0){B}([nodesep=3,angle=-60]{A}B){C}
    \pstMarkAngle{B}{A}{C}{1}
    \pstMarkAngle{C}{B}{A}{2}
    \pstMarkAngle{A}{C}{B}{3}
    \ncline[offset=15pt,linestyle=none]{A}{C}\ncput[npos=\n]{$F=$}
\end{pspicture}}
\end{document}