er_group</code></a> ‚Äî <span class="docstring-category">Method</span></header><section><div><p><code>coxeter_group(C)</code> or <code>coxgroup(C)</code></p><p><code>C</code>  should be  a square  matrix of  integers, rationals or real cyclotomic numbers.  The function returns the Coxeter group whose Cartan matrix is <code>C</code> as  a matrix group with generators the  following reflections: let <code>V</code> be a real  vector space of  dimension <code>size(C,1)</code> and  let <code>e·µ¢</code> b