[main12_7] eigenvalue measure ezcontour;
main12_3 test with 60deg and 80deg line segments (defined in main12_7)
[main12_7] simplified distance calculation
[main12_7] plot the derivatives of f
[main12_7] plot where the derivatives of f become zero
[main12_7] axis equal
[main12_7] xmin, xmax, eps variables added
[main12_7] plot min max lines
[main12_7] derivatives equal zero plotted in one figure