function drawline (C, alpha)
%DRAWLINE
%
%       drawline(C, alpha)
%       draws line through C.

  s = sin(alpha); c = cos(alpha);
  Q =[c -s; s c];
  theta = [-10:0.2:10];
  u = diag(C)*ones(2,length(theta)) + ...
       Q*[sin(theta); cos(theta)];
  plot(u(1,:),u(2,:));

end % drawline

