rec-root1

a to the nth power

W3C sample	WIRIS
	$\sqrt[n]{a}$

<math xmlns="http://www.w3.org/1998/Math/MathML">
  <apply>
    <root/>
    <degree>
      <ci type="integer">n</ci>
    </degree>
    <ci>a</ci>
  </apply>
</math>

Author: MathML 2 Recommendation