rea
          </p>
<h6>
<a name="geometry.reference.algorithms.area.area_1.h4"></a>
            <span><a name="geometry.reference.algorithms.area.area_1.header"></a></span><a class="link" href="area_1.html#geometry.reference.algorithms.area.area_1.header">Header</a>
          </h6>
<p>
            Either
          </p>
<p>
            <code class="computeroutput"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><sp