Example 5.  Use cubic spline quadrature to compute a numerical approximation to the integral [Graphics:Images/SplineQuadMod_gr_187.gif].  
Use the tolerances [Graphics:Images/SplineQuadMod_gr_188.gif].  Compare with the analytic or "true value" of the integral.

Solution 5.

5 (a). Plot the function over the interval  [0, 3].

[Graphics:../Images/SplineQuadMod_gr_189.gif]

[Graphics:../Images/SplineQuadMod_gr_190.gif]

[Graphics:../Images/SplineQuadMod_gr_191.gif]

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

[Graphics:../Images/SplineQuadMod_gr_192.gif]

[Graphics:../Images/SplineQuadMod_gr_193.gif]
[Graphics:../Images/SplineQuadMod_gr_194.gif]

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

[Graphics:../Images/SplineQuadMod_gr_195.gif]

[Graphics:../Images/SplineQuadMod_gr_196.gif]
[Graphics:../Images/SplineQuadMod_gr_197.gif]

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

[Graphics:../Images/SplineQuadMod_gr_198.gif]

[Graphics:../Images/SplineQuadMod_gr_199.gif]
[Graphics:../Images/SplineQuadMod_gr_200.gif]

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

[Graphics:../Images/SplineQuadMod_gr_201.gif]

[Graphics:../Images/SplineQuadMod_gr_202.gif]
[Graphics:../Images/SplineQuadMod_gr_203.gif]

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

[Graphics:../Images/SplineQuadMod_gr_204.gif]

m sample points

[Graphics:../Images/SplineQuadMod_gr_205.gif]

11

[Graphics:../Images/SplineQuadMod_gr_206.gif]

21

[Graphics:../Images/SplineQuadMod_gr_207.gif]

41

[Graphics:../Images/SplineQuadMod_gr_208.gif]

81

[Graphics:../Images/SplineQuadMod_gr_209.gif]

 

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

[Graphics:../Images/SplineQuadMod_gr_210.gif]


[Graphics:../Images/SplineQuadMod_gr_211.gif]
[Graphics:../Images/SplineQuadMod_gr_212.gif]
[Graphics:../Images/SplineQuadMod_gr_213.gif]
[Graphics:../Images/SplineQuadMod_gr_214.gif]
[Graphics:../Images/SplineQuadMod_gr_215.gif]
[Graphics:../Images/SplineQuadMod_gr_216.gif]
[Graphics:../Images/SplineQuadMod_gr_217.gif]
[Graphics:../Images/SplineQuadMod_gr_218.gif]

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

[Graphics:../Images/SplineQuadMod_gr_219.gif]


[Graphics:../Images/SplineQuadMod_gr_220.gif]
[Graphics:../Images/SplineQuadMod_gr_221.gif]


[Graphics:../Images/SplineQuadMod_gr_222.gif]

[Graphics:../Images/SplineQuadMod_gr_223.gif]

[Graphics:../Images/SplineQuadMod_gr_224.gif]
[Graphics:../Images/SplineQuadMod_gr_225.gif]
[Graphics:../Images/SplineQuadMod_gr_226.gif]
[Graphics:../Images/SplineQuadMod_gr_227.gif]

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(c) John H. Mathews 2004