plot2d ([[parametric,cos(t),sin(t), [t,0,2*%pi]], -abs(x)],
  [x,-sqrt(2),sqrt(2)], same_xy, [pdf_file,"./plotting12.pdf"]);
plot2d ([[parametric,cos(t),sin(t), [t,0,2*%pi]], -abs(x)],
  [x,-sqrt(2),sqrt(2)], same_xy, [png_file,"./plotting12.png"]);
