 are transformed by
<p>
<i>R</i>* = <i>T R</i>, <i>S</i>* = <i>T S T<sup>-1</sup></i>.
<p>
where <i>T</i> is the orthogonal rotation matrix
<p>
<img align=bottom src="../equations/Trot.gif">
<p>
The special value psi = pi/2 represents a bend down.

<center>
<a name=rbend><img align=bottom src="../figures/ref_rbend.gif"></a>
<p>
<b>Figure 2:</b> Reference System for Rectangular Bends;
The signs of the pole-face rotations are positive as shown.
</center>

<center>
<a name=sbend><img align=bottom src="../figur