Example 7.  Plot the absolute error  [Graphics:Images/NumericalDiffMod_gr_175.gif]  over the interval  [Graphics:Images/NumericalDiffMod_gr_176.gif],  and estimate the maximum absolute error over the interval.  
7 (a).  Compute the error bound  [Graphics:Images/NumericalDiffMod_gr_177.gif]  and observe that  [Graphics:Images/NumericalDiffMod_gr_178.gif]  over  [Graphics:Images/NumericalDiffMod_gr_179.gif].  
7 (b).  Since the function f[x] and its derivative is well known, and we have the graph for [Graphics:Images/NumericalDiffMod_gr_180.gif],  we can observe that the maximum error on the given interval occurs at x=0.  Thus we can do better that "theory", we see that [Graphics:Images/NumericalDiffMod_gr_181.gif]  over  [Graphics:Images/NumericalDiffMod_gr_182.gif].

Solution 7.

7 (a).  Compute the error bound  [Graphics:../Images/NumericalDiffMod_gr_183.gif]  and observe that  [Graphics:../Images/NumericalDiffMod_gr_184.gif]  over  [Graphics:../Images/NumericalDiffMod_gr_185.gif].  

[Graphics:../Images/NumericalDiffMod_gr_186.gif]


[Graphics:../Images/NumericalDiffMod_gr_187.gif]

[Graphics:../Images/NumericalDiffMod_gr_188.gif]
[Graphics:../Images/NumericalDiffMod_gr_189.gif]
[Graphics:../Images/NumericalDiffMod_gr_190.gif]
[Graphics:../Images/NumericalDiffMod_gr_191.gif]
[Graphics:../Images/NumericalDiffMod_gr_192.gif]

7 (b).  Since we the function f[x] and its derivative is well known, and we have the graph for [Graphics:../Images/NumericalDiffMod_gr_193.gif],  we can observe that the maximum error on the given interval occurs at  [Graphics:../Images/NumericalDiffMod_gr_194.gif].  Usually we can do better that "theory", with [Graphics:../Images/NumericalDiffMod_gr_195.gif]  over  [Graphics:../Images/NumericalDiffMod_gr_196.gif]. However, the two bounds are nearly the same for this example.

[Graphics:../Images/NumericalDiffMod_gr_197.gif]


[Graphics:../Images/NumericalDiffMod_gr_198.gif]

[Graphics:../Images/NumericalDiffMod_gr_199.gif]
[Graphics:../Images/NumericalDiffMod_gr_200.gif]
[Graphics:../Images/NumericalDiffMod_gr_201.gif]
[Graphics:../Images/NumericalDiffMod_gr_202.gif]

Remark. Is there a difference between the error bound and minimal error bound?  It looks different i the 10 decimal place to me.  It was hard to get it too.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(c) John H. Mathews 2004