>> drvb
---------------- 11.2.3 a ----------------
it=  0, z=-0.1666667, phi=  7.4898e-02
it=  1, z=-0.2503546, phi= -3.1549e-04
it=  2, z=-0.2500051, phi= -6.3503e-09
  t           y      y true
1.0  0.50000000  0.50000000
1.2  0.45454618  0.45454545
1.4  0.41666752  0.41666667
1.6  0.38461607  0.38461538
1.8  0.35714323  0.35714286
2.0  0.33333333  0.33333333
---------------- 11.2.3 b ----------------
it=  0, z= 0.5000000, phi=  4.0955e+01
it=  1, z= 0.3842470, phi=  1.6131e+01
it=  2, z= 0.2523326, phi=  6.0554e+00
it=  3, z= 0.1198815, phi=  1.9112e+00
it=  4, z= 0.0289893, phi=  3.6810e-01
it=  5, z= 0.0020521, phi=  2.0387e-02
it=  6, z= 0.0003799, phi=  7.0127e-05
  t           y      y true
1.0  2.00000000  2.00000000
1.2  2.03369066  2.03333333
1.4  2.11466252  2.11428571
1.6  2.22530754  2.22500000
1.8  2.35576849  2.35555556
2.0  2.50007013  2.50000000
---------------- 11.2.3 c ----------------
it=  0, z= 0.2387984, phi= -2.2428e-02
it=  1, z= 0.2500275, phi=  6.5475e-05
  t           y      y true
2.0  1.19314718  1.19314718
2.2  1.24301046  1.24300281
2.4  1.29215244  1.29213540
2.6  1.34015591  1.34012683
2.8  1.38680709  1.38676227
3.0  1.43201110  1.43194562