Derivatives and Integrals: An Annotated Discourse

<section label="section-units-measure">
  <title>Units of Measure</title>
  <p>
    Units of measure can be given xml treatment too with the <c>quantity</c> element.
    In <latex />, the <c>siunitx</c>
        <idx><h>siunitx package</h></idx>
        <idx><h>package</h><h>siunitx</h></idx>
        <idx><h>units</h></idx>
    package is loaded to achive unit handling.
    Since that package only offers SI units,
    some other common units will be added by <pretext /> in the preamble.
    In HTML, the capabilities of <c>siunitx</c> are simulated, weakly.
    Note that at present,
    you should not attempt to use the <c>quantity</c> element within a math environment.
  </p>
  <p>
    The value of gravitational constant <m>g</m> is
    <quantity>
      <mag>9.8</mag><unit base="meter" /><per base="second" exp="2" />
    </quantity>.
    Force is measured in
    <quantity>
      <unit prefix="kilo" base="gram" /><unit base="meter" /><per base="second" exp="2" />
    </quantity>, also known as one
    <quantity>
      <unit base="newton" />
    </quantity>.
    A quantity with rather ridiculous units is
    <quantity>
      <mag>23</mag><unit prefix="micro" base="hectare" exp="23" /><per base="degreeCelsius" /><per base="second" exp="2" />
    </quantity>.
    One
    <quantity>
      <unit base="hertz" />
    </quantity>
    is the same as
    <quantity>
      <per base="second" />
    </quantity>.
    You can have a unitless quantity, like
    <quantity>
      <mag>42</mag>
    </quantity>, which may help with consistency between such numbers and units in the <latex /> output.
    Some non-SI units are available, such as the absurd
    <quantity>
      <unit base="degreeFahrenheit" /><unit base="foot" /><unit base="pound" /><per base="gallon" />
    </quantity>.
    The <latex /> command <c>\pi</c> is recognized within <c>mag</c> in conversions to HTML, which is consistent with the behavior with a conversion to <latex />, for example there are
    <quantity>
      <mag>2\pi</mag> <unit base="radian" />
    </quantity>
    in a full circle.
    This is a similar quantity with multiple occurences of <c>\pi</c> to test a particular template used for HTML output.
    It is not meant to make any sense:
    <quantity>
      <mag>21\pi45\pi234\pi890</mag> <unit base="radian" />
    </quantity>.
  </p>
  <p>
    For a full list of the allowed units and prefixes,
    see <c>pretext-units.xsl</c>.
    If you have a need for more units,
    they need to be added to <c>pretext-units.xsl</c> in the section that deals with units which are not part of <c>siunitx</c> by default.
    Note that the <c>mag</c> element should come first,
    followed by the <c>unit</c> element,
    followed by the <c>per</c> element.
  </p>
</section>