boost_1_45_0/libs/math/doc/sf_and_dist/equations/beta4.mml

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
  <mrow>
    <mtext>beta</mtext>
    <mfenced>
      <mrow>
        <mi>a</mi>
        <mo>,</mo>
        <mi>b</mi>
      </mrow>
    </mfenced>
    <mo>=</mo>
    <mfrac>
      <mfenced>
        <mrow>
          <mi>a</mi>
          <mo>+</mo>
          <mi>b</mi>
        </mrow>
      </mfenced>
      <mi>b</mi>
    </mfrac>
    <mtext>beta</mtext>
    <mfenced>
      <mrow>
        <mi>a</mi>
        <mo>,</mo>
        <mi>b</mi>
        <mo>+</mo>
        <mn>1</mn>
      </mrow>
    </mfenced>
  </mrow>
</math>