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Adding LaTeX Equations in DITA Topics

LaTeX is a high-quality typesetting system that includes features designed for the production of technical and scientific documentation. LaTeX can also be used to express mathematical formulas in a textual format. By default, web browsers and PDF readers do not have support to show mathematical equations written in LaTeX, but there are open-source projects that can read LaTeX and convert it to other image types.

Adding support for writing LaTeX equations in a DITA topic implies three stages:

Find a way to write the equation in the DITA XML content. You can either create a DITA DTD specialization and add a new element (for example, called <latex> and it extends the DITA <foreign> element). Alternatively, you can directly use the DITA <foreign> element with a specific @outputclass attribute value:
```
<!DOCTYPE topic PUBLIC "-//OASIS//DTD DITA Topic//EN" "topic.dtd">
<topic id="testEquation">
  <title>Test equation</title>
  <body>
    <p><foreign outputclass="embed-latex">L' = {L}{\sqrt{1-\frac{v^2}{c^2}}}</foreign></p>
  </body>
</topic>
```
If you want Oxygen XML Author to properly present the LaTeX equation when editing in the Author visual mode, you need a plugin that converts the equation content to an image. There is a sample plugin that does that here: https://github.com/oxygenxml/wsaccess-javascript-sample-plugins/tree/master/latex-images-support. You can download and copy the plugin folder latex-images-support to the Oxygen XML Author plugins folder, then restart Oxygen XML Author.
The final stage would be to publish the content to HTML-based or PDF output. The following DITA Open Toolkit plugin automatically converts LaTeX images to SVG when publishing: https://github.com/oxygenxml/dita-latex.