Example 2.  Use cubic spline quadrature to compute a numerical approximation to the integral  [Graphics:Images/SplineQuadMod_gr_67.gif].  
Use the tolerances [Graphics:Images/SplineQuadMod_gr_68.gif].  Compare with the analytic or "true value" of the integral.

Solution 2.

[Graphics:../Images/SplineQuadMod_gr_69.gif]
[Graphics:../Images/SplineQuadMod_gr_70.gif]

2 (a). Plot the function over the interval  [0, 2].

[Graphics:../Images/SplineQuadMod_gr_71.gif]

[Graphics:../Images/SplineQuadMod_gr_72.gif]

[Graphics:../Images/SplineQuadMod_gr_73.gif]

2 (b). Construct the cubic spline for 11 nodes and use it for quadrature.

[Graphics:../Images/SplineQuadMod_gr_74.gif]

[Graphics:../Images/SplineQuadMod_gr_75.gif]
[Graphics:../Images/SplineQuadMod_gr_76.gif]

2 (c). Construct the cubic spline for 21 nodes and use it for quadrature.

[Graphics:../Images/SplineQuadMod_gr_77.gif]

[Graphics:../Images/SplineQuadMod_gr_78.gif]
[Graphics:../Images/SplineQuadMod_gr_79.gif]

2 (d). Construct the cubic spline for 41 nodes and use it for quadrature.

[Graphics:../Images/SplineQuadMod_gr_80.gif]

[Graphics:../Images/SplineQuadMod_gr_81.gif]
[Graphics:../Images/SplineQuadMod_gr_82.gif]

2 (e). Construct the cubic spline for 41 nodes and use it for quadrature.

[Graphics:../Images/SplineQuadMod_gr_83.gif]

[Graphics:../Images/SplineQuadMod_gr_84.gif]
[Graphics:../Images/SplineQuadMod_gr_85.gif]

2 (f). Compare the results from parts b-d.

[Graphics:../Images/SplineQuadMod_gr_86.gif]

m sample points

[Graphics:../Images/SplineQuadMod_gr_87.gif]

11

[Graphics:../Images/SplineQuadMod_gr_88.gif]

21

[Graphics:../Images/SplineQuadMod_gr_89.gif]

41

[Graphics:../Images/SplineQuadMod_gr_90.gif]

81

[Graphics:../Images/SplineQuadMod_gr_91.gif]

 

2 (g). Use Mathematica to find the analytic solution to the integral, i.e. the "true value" of the integral.

[Graphics:../Images/SplineQuadMod_gr_92.gif]


[Graphics:../Images/SplineQuadMod_gr_93.gif]
[Graphics:../Images/SplineQuadMod_gr_94.gif]
[Graphics:../Images/SplineQuadMod_gr_95.gif]
[Graphics:../Images/SplineQuadMod_gr_96.gif]
[Graphics:../Images/SplineQuadMod_gr_97.gif]
[Graphics:../Images/SplineQuadMod_gr_98.gif]
[Graphics:../Images/SplineQuadMod_gr_99.gif]
[Graphics:../Images/SplineQuadMod_gr_100.gif]

2 (h). How close did our last numerical approximation using Romberg integration come to the "true value" of the integral.

[Graphics:../Images/SplineQuadMod_gr_101.gif]


[Graphics:../Images/SplineQuadMod_gr_102.gif]
[Graphics:../Images/SplineQuadMod_gr_103.gif]


[Graphics:../Images/SplineQuadMod_gr_104.gif]

[Graphics:../Images/SplineQuadMod_gr_105.gif]

[Graphics:../Images/SplineQuadMod_gr_106.gif]
[Graphics:../Images/SplineQuadMod_gr_107.gif]
[Graphics:../Images/SplineQuadMod_gr_108.gif]
[Graphics:../Images/SplineQuadMod_gr_109.gif]

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(c) John H. Mathews 2004