range <code class="literal">[0;+&#8734;[</code>, and therefore
        both have inverses. The hyperbolic cosine is one to one from <code class="literal">]-&#8734;;+1[</code>
        onto <code class="literal">]-&#8734;;-1[</code> (and from <code class="literal">]+1;+&#8734;[</code> onto
        <code class="literal">]-&#8734;;-1[</code>); the inverse function we use here is defined on
        <code class="literal">]-&#8734;;-1[</code> with range <code class="literal">]-&#8734;;+1[</code>.
      </p>
<p>
  