maction-02

You should see fraction n!/k!(n-k)! once you place mouse pointer over math expression below

W3C sample	WIRIS
	$$\left(\begin{array}{c}n\\ k\end{array}\right)\frac{n!}{k!(n-k)!}$$

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
  <maction actiontype="tooltip">
    <mrow>
      <mfenced>
        <mrow>
          <mtable>
            <mtr>
              <mtd>
                <mi>n</mi>
              </mtd>
            </mtr>
            <mtr>
              <mtd>
                <mi>k</mi>
              </mtd>
            </mtr>
          </mtable>
        </mrow>
      </mfenced>
    </mrow>
    <mrow>
      <mfrac>
        <mrow>
          <mi>n</mi>
          <mo form="postfix">!</mo>
        </mrow>
        <mrow>
          <mi>k</mi>
          <mo form="postfix">!</mo>
          <mo fence="true">(</mo>
          <mi>n</mi>
          <mo>−</mo>
          <mi>k</mi>
          <mo fence="true">)</mo>
          <mo form="postfix">!</mo>
        </mrow>
      </mfrac>
    </mrow>
  </maction>
</math>

Author: George Chavchanidze, Opera Software ASA