
<!DOCTYPE math
  PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<math xmlns="http://www.w3.org/1998/Math/MathML">
<apply>
  <partialdiff/>
  <bvar>
    <ci> x </ci>
    <degree>
      <ci> n </ci>
    </degree>
  </bvar>
  <bvar>
    <ci> y </ci>
    <degree>
      <ci> m </ci>
    </degree>
  </bvar>
  <apply><sin/>
    <apply> <times/>
      <ci> x </ci>
      <ci> y </ci>
    </apply>
  </apply>
</apply>
</math>
