es.
      The first of these, <span class="emphasis"><em>theta</em></span> has a natural range of -pi to
      +pi, and the other two have natural ranges of -pi/2 to +pi/2 (as is the case
      with the usual spherical coordinates in <span class="emphasis"><em><span class="bold"><strong>R<sup>3</sup></strong></span></em></span>).
      Due to the many symmetries and periodicities, nothing untoward happens if the
      magnitude is negative or the angles are outside their natural ranges. The expected
      d