rec-notanumber1

NaN

W3C sample WIRIS
[N/A] eq divide 0 0 NaN 
<math xmlns="http://www.w3.org/1998/Math/MathML">
  <apply>
    <csymbol cd="relation1">eq</csymbol>
    <apply>
      <csymbol cd="arith1">divide</csymbol>
      <cn>0</cn>
      <cn>0</cn>
    </apply>
    <csymbol cd="nums1">NaN</csymbol>
  </apply>
</math>

Author: MathML 2 Recommendation