Define prefix and namespace URI binding and default namespace:
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:mml="http://www.w3.org/1998/Math/MathML">
Use MathML inline in XHTML document:
<p>In order to mix XHTML and MathML, we need to include the proper DTD and also pay attention to XML namespaces!</p> <mml:math> <mml:mtext>The roots of the quadratic equation</mml:mtext> <mml:mspace width="2em"/> <mml:mi>a</mml:mi> <mml:mo>⁢</mml:mo> <mml:msup> <!-- content removed for clarity -->