# Typesetting triangular 2cells in xypic

I would like to typeset the diagram below in xypic.

Unforunately, I have no idea how to do this, and I find it impossible to figure out how to actually use the 2cell extension for xypic.

The best I'm managing is:

Given by

\documentclass[oneside,american,oldfontcommands,all,cmtip]{memoir}
\usepackage{xy}
\xyoption{2cell}
\UseAllTwocells

\begin{document}
$\xymatrix{\cdot\ar[dr]\\ & \cdot\ulcompositemap<4.8> }$

\end{document}


I also don't know how to adapt the answers to this question. Particularly, the answers resolve the 2cell on the right, but the arrow is parallel to the southwest arrow, so I can't resolve the 2cell on the left.

• Please provide a complete compilable minimal working example (MWE) showing everything you got so far. – Skillmon Sep 13 '17 at 11:13

An example with tikz-cd intead of xymatrix. It is more easy.

\documentclass{article}
\usepackage{tikz-cd}

\usepackage{mathtools}
\newcommand{\rin}{\rotatebox[origin=c]{45}{$\Rightarrow$}}
\begin{document}
\begin{tikzcd}
& \cdot \arrow[ld, "\rin"] \arrow[d] \arrow[rd, "\rin"'] &  \\
\cdot \arrow[r] & \cdot \arrow[r] & \cdot
\end{tikzcd}
\end{document}


Here is a solution using xy and txfonts for arrows.

\documentclass[oneside,american,oldfontcommands,all,cmtip]{memoir}
\usepackage[all]{xy}
\usepackage{amsmath,txfonts}

\begin{document}

$\xymatrix{ & \bullet \ar[dl] \ar[d] \ar[dr] & \\ \bullet \ar[r] & \bullet \ar[r] \ar@{}[lu]|(.25){\Nearrow} \ar@{}[ru]|(.25){\Nearrow}& \bullet }$

\end{document}


Update: Here is a solution using the graphicx to rotate the standard \Rightarrow (so no txfonts required as above).

\documentclass[oneside,american,oldfontcommands,all,cmtip]{memoir}
\usepackage[all]{xy}
\usepackage{amsmath}
\usepackage{graphicx}
\newcommand{\implication}{\rotatebox[origin=c]{45}{$\Rightarrow$}}

\begin{document}

$\xymatrix{ & \bullet \ar[dl] \ar[d] \ar[dr] & \\ \bullet \ar[r] & \bullet \ar[r] \ar@{}[lu]|(.25){\implication} \ar@{}[ru]|(.25){\implication}& \bullet }$

\end{document}