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<p>the proof.</p>

<p><b>Topological proof of the base case</b></p>

<p>Let , and consider the cover. Since the intersection of convex sets is convex, every non-empty finite intersection of elements of  is contractible. Hence  is a <a href="page.php?w=good_cover">good cover</a>.</p>

<p>By the basic <a href="page.php?w=nerve_theorem">nerve lemma</a>,  is homotopy equivalent to the geometric realization  of the nerve  of the cover. Assuming that</p>

<p>the nerve  is the boundary complex of the simplex  consisting of all the -faces. Therefore  is</p><p>
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