How to draw a triangle with a number in it?

Question

I would like to draw some shapes (triangle, circle and both triangle and circle) with numbers in it, if this is possible

Answer 1

I am pretty sure that this post at texample.net might help you a lot. Here I report a little snippet that may help you getting started:

% Regular polygons
\documentclass{article}
\usepackage{tikz}

\begin{document}

% Radius of regular polygons
\newdimen\R
\R=2cm

\begin{tikzpicture}
    % Triangle
    \draw (0:\R) \foreach \x in {120,240} {
        -- (\x:\R)
    } -- cycle (90:\R);
    \node[align=center] {Triangle};

    % Circle
    \draw (5,0) circle (\R) node[align=center] {Circle};
\end{tikzpicture}

\end{document}

That produces the following output:

Of course, you can draw a circle around a triangle by simply indicating the same starting coordinate for both shapes. Just tinker with the parameters and try to find what best suits your needs.