rec-exists1

there exists an x for which f(x)=0

W3C sample	WIRIS
	$x f x 0$

<math xmlns="http://www.w3.org/1998/Math/MathML">
  <apply>
    <exists/>
    <bvar>
      <ci>x</ci>
    </bvar>
    <apply>
      <eq/>
      <apply>
        <fn>
          <ci>f</ci>
        </fn>
        <ci>x</ci>
      </apply>
      <cn>0</cn>
    </apply>
  </apply>
</math>

Author: MathML 2 Recommendation