Example 3.  Find the dominant eigenvalue and eigenvector for the matrix  [Graphics:Images/PowerMethodMod_gr_216.gif].  
Use the shift  [Graphics:Images/PowerMethodMod_gr_217.gif] in the shifted inverse power method.

Solution 3.

[Graphics:../Images/PowerMethodMod_gr_218.gif]



[Graphics:../Images/PowerMethodMod_gr_219.gif]

[Graphics:../Images/PowerMethodMod_gr_220.gif]

[Graphics:../Images/PowerMethodMod_gr_221.gif]
[Graphics:../Images/PowerMethodMod_gr_222.gif]
[Graphics:../Images/PowerMethodMod_gr_223.gif]
[Graphics:../Images/PowerMethodMod_gr_224.gif]
[Graphics:../Images/PowerMethodMod_gr_225.gif]
[Graphics:../Images/PowerMethodMod_gr_226.gif]
[Graphics:../Images/PowerMethodMod_gr_227.gif]
[Graphics:../Images/PowerMethodMod_gr_228.gif]
[Graphics:../Images/PowerMethodMod_gr_229.gif]
[Graphics:../Images/PowerMethodMod_gr_230.gif]



[Graphics:../Images/PowerMethodMod_gr_231.gif]



[Graphics:../Images/PowerMethodMod_gr_232.gif]

[Graphics:../Images/PowerMethodMod_gr_233.gif]

[Graphics:../Images/PowerMethodMod_gr_234.gif]

[Graphics:../Images/PowerMethodMod_gr_235.gif]

That is [Graphics:../Images/PowerMethodMod_gr_236.gif] close to the dominant eigenvalue  [Graphics:../Images/PowerMethodMod_gr_237.gif]  and corresponding eigenvector  [Graphics:../Images/PowerMethodMod_gr_238.gif].  

Now check our work.

[Graphics:../Images/PowerMethodMod_gr_239.gif]



[Graphics:../Images/PowerMethodMod_gr_240.gif]

[Graphics:../Images/PowerMethodMod_gr_241.gif]

[Graphics:../Images/PowerMethodMod_gr_242.gif]

[Graphics:../Images/PowerMethodMod_gr_243.gif]

[Graphics:../Images/PowerMethodMod_gr_244.gif]

Compare with Mathematica's Eigensystem procedure.  Observe that Mathematica returns unit length eigenvectors.

[Graphics:../Images/PowerMethodMod_gr_245.gif]



[Graphics:../Images/PowerMethodMod_gr_246.gif]

[Graphics:../Images/PowerMethodMod_gr_247.gif]

[Graphics:../Images/PowerMethodMod_gr_248.gif]

[Graphics:../Images/PowerMethodMod_gr_249.gif]

[Graphics:../Images/PowerMethodMod_gr_250.gif]

[Graphics:../Images/PowerMethodMod_gr_251.gif]

[Graphics:../Images/PowerMethodMod_gr_252.gif]

[Graphics:../Images/PowerMethodMod_gr_253.gif]

Notice.  The numerical eigenvector found by Mathematica is [Graphics:../Images/PowerMethodMod_gr_254.gif] which is a multiple of the the eigenvector [Graphics:../Images/PowerMethodMod_gr_255.gif]  found by the power method, i.e.

        [Graphics:../Images/PowerMethodMod_gr_256.gif]

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(c) John H. Mathews 2004