To draw a graph like this, what code do I need?

Question

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{calc}
\usetikzlibrary{intersections}
\begin{document}
    \begin{tikzpicture}[scale=5]
        \coordinate[label=above left:$A$] (A) at (95:1);
        \coordinate[label=below left:$B$] (B) at (200:1);
        \coordinate[label=below left:$D$] (D) at (-110:1);
        \coordinate[label=below right:$C$] (C) at (-60:1);
        \draw[name path=circ] (0,0) circle (1);
        \path[name path=AC] (A) -- ($(A)!1.2!30:(B)$);
%         \path[name path=AC] (D) -- ($(D)!1.2!-15:(B)$);
%         \path[name intersections={of=AC and circ, by={[label=below right:$C$]C}}];
%         \path[name intersections={of=BD and circ, by={[label=above right:$D$]D}}];
        \draw[line join=bevel] (A) -- (B) --  cycle;
        \draw[line join=bevel] (A) -- (D) --  cycle;
        \draw[line join=bevel] (A) -- (C) --  cycle;
        \draw[line join=bevel] (D) -- (C) --  cycle;
        \draw[line join=bevel] (B) -- (D) --  cycle;
    \end{tikzpicture}
\end{document}

please make your code as complete small document with \documentclass{...} on the start and\end{document}on the and. Also add all necessarytikzlibraries`. — Zarko, Oct 27 '16 at 12:51
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score 9 · Answer 1 · edited Oct 28 '16 at 11:39

Have a look at the following code:

\documentclass{article}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}[scale=5]
\draw[blue] (0,0) circle (1);
\node[circle, fill=orange, label=above left  :$A$] (A) at (95:1) {};
        \coordinate[label=below left  :$B$] (B) at (200:1);
        \coordinate[label=below left  :$D$] (D) at (-110:1);
        \coordinate[label=below right :$C$] (C) at (-60:1);
        \draw[blue] (A) -- (B) ;
        \draw[blue] (A) -- (D) ;
        \draw[blue] (A) -- (C) ;
        \draw[blue,shorten <= -30,shorten >= -30] (D) -- (C);
        \draw[blue] (B) -- (D)  node[midway,above,font=\tiny,color=black]{$\theta_{1}$};
\end{tikzpicture}
\end{document}

compiling it gives

This is not exactly what you want but you have all the elements in hand to obtain exactly what you want.

No need to say thanks just approve the answer, if you were helped. This is the way the site works. — Denis, Oct 27 '16 at 13:54

score 8 · Answer 2 · answered Oct 28 '16 at 09:00

A version in Metapost, wrapped up in luamplib. Compile with lualatex.

\RequirePackage{luatex85}
\documentclass[border=5mm]{standalone}
\usepackage{luamplib}
\begin{document}
\mplibtextextlabel{enable}
\begin{mplibcode}
beginfig(1);

    path circ;
    pair A,B,C,D;

    circ = fullcircle scaled 8cm;
    A = point   95*8/360 of circ;
    B = point  200*8/360 of circ;
    C = point  -60*8/360 of circ;
    D = point -110*8/360 of circ;

    drawoptions(withcolor 1/3[blue,white]);

    draw circ;
    draw A--B;
    draw A--C;
    draw A--D;

    draw (-1/4)[B,D] -- 5/4[B,D];
    draw (-1/4)[C,D] -- 5/4[C,D];

    drawoptions();

    forsuffixes @=A,B,C,D:
       label("$" & str @ & "$", @ scaled 10/9);
       fill fullcircle scaled dotlabeldiam shifted @ withcolor red+1/2green;
    endfor

    label.urt("$e_1$", 1/2[B,D]);
    label.top("$e_2$", 1/2[C,D]);

endfig;
\end{mplibcode}
\end{document}

Notes

These lines

 draw (-1/4)[B,D] -- 5/4[B,D];
 draw (-1/4)[C,D] -- 5/4[C,D];

show you one simple way to draw lines "through" two points with Metapost, using the mediation syntax. In general f[a,b] gives you a point on the line through a and b where f is a fraction of the distance from a to b, so 1/2[a,b] gives you the mid point, and so on.

But note that you need the parentheses round the negative mediant to stop MP interpreting it as -(1/4[B,D]) which is not the point you want. I could also have written

draw 5/4[D,B] -- 5/4[B,D];
draw 5/4[D,C] -- 5/4[C,D];

to avoid the problem. More beautiful perhaps but also harder to follow.

The forsuffixes loop uses @ as the loop variable. The scaled trick to position the labels only works because the diagram is centred at the origin.

To draw a graph like this, what code do I need?

2 Answers2

Notes

Linked