Building a tree

A very common type of hierarchical graph is a tree. Tree nodes have children. These are connected by edges and are usually displayed in rows when growing down, or in columns when growing horizontally.

We will draw a tree presenting possible math formula layouts.

How to do it...

We will use basic TikZ, without any extra package. Follow these steps:

1. Start with a document class:

   \documentclass{article}

2. Load the tikz package:

   \usepackage{tikz}

3. Start the document:

   \begin{document}

4. Begin with a TikZ picture, and specify some options for it:

   \begin{tikzpicture}[sibling distance=10em,
     every node/.style = {shape=rectangle, rounded corners,
       draw, align=center,
       top color=white, bottom color=blue!20}]]

5. Draw a node and add children to it:

     \node {Formulas}
       child { node {single-line} }
       child { node {multi-line}
         child { node {aligned at}
           child { node {relation sign} }
           child { node {several places} }
           child { node {center} } }
         child { node {first...