<?xml version="1.0" encoding='utf-8'?>
<!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.1//EN" "http://www.wapforum.org/DTD/wml_1.1.xml">
<wml>
<card id="card1" title="Opaque set - Page 8 - Wikipedia">
<p>
<a accesskey="1" href="page.php?w=Opaque_set&amp;p=7">1.Previous</a><br />
<a accesskey="3" href="page.php?w=Opaque_set&amp;p=9">3.Next</a>
</p>
<p>respectively. When this is not specified, the barrier is assumed to have no constraints on its location. Versions of the problem in which the opaque set must be connected or form a single curve have also been considered. It is not known whether every <a href="page.php?w=convex_set">convex set</a>  has a shortest opaque set, or whether instead the lengths of its opaque sets might approach an <a href="page.php?w=infimum">infimum</a> without ever reaching it. Every opaque set for  can be approximated arbitrarily closely in length by an opaque forest,</p><p>
<a accesskey="1" href="page.php?w=Opaque_set&amp;p=7">1.Previous</a><br />
<a accesskey="3" href="page.php?w=Opaque_set&amp;p=9">3.Next</a>
</p>

<do type="prev" label="Search">
        <go href="search.wml"/>
</do>

</card>
</wml>
