function  w = xpz(xy,t,u)
%XPZ    z-coordinate of t-point of xy-curve rotated through angle u.
%   XPZ is a helper function used by TUBE.
 
%   C. Henry Edwards, University of Georgia. 6-20-93.
%
%   Copyright 1984-2000 The MathWorks, Inc. 
%   $Revision: 5.8 $  $Date: 2000/06/01 03:46:30 $

[xt,yt] = feval(xy,t);

w = xt.*sin(u) + yt.*cos(u);
