Solving for Eigenvectors of an Already Diagonalized Matrix












0












$begingroup$


I'm a bit stuck in solving for the eigenvectors of the following equation.
begin{align}
begin{bmatrix}
2m+M-2komega & 0
\
0 & dfrac{1}{12}Ml^2 + dfrac{1}{2}ml^2 - dfrac{k}{2}l^2omega
end{bmatrix}
begin{bmatrix}
a_1 \ a_2
end{bmatrix}
=0
end{align}



I found the eigenvalues using Mathematica, but finding the Eigenvectors was problematic, so I attempted it by hand. The eigenvalues are:
begin{align}
omega_1=dfrac{3m}{2k} , omega_2 = dfrac{6m+M}{6k}
end{align}



In solving for the eigenvector corresponding to $omega_1$, I get to the following equation.



begin{align}
begin{bmatrix}
M-m & 0
\
0 & dfrac{1}{12}Ml^2 - dfrac{1}{6}ml^2
end{bmatrix}
begin{bmatrix}
a_1 \ a_2
end{bmatrix}
=0
end{align}



I'm totally unsure on how to solve this for the eigenvector. Essentially, my confusion lies in both $a_1$ and $a_2$ equal to zero here, since there are no off-diagonal terms.



Any help would be appreciated, thank you.










share|cite|improve this question









$endgroup$








  • 4




    $begingroup$
    If $$ D = begin{bmatrix} a & 0 \ 0 & bend{bmatrix},$$ then clearly $[1,0]^T, [0,1]^T$ are eigenvectors belong to $a,b$ respectively.
    $endgroup$
    – xbh
    Nov 29 '18 at 8:36










  • $begingroup$
    @xbh Can you explain this in further detail?
    $endgroup$
    – Kosta
    Nov 29 '18 at 8:37










  • $begingroup$
    That claim is pretty obvious by verifying the definition $Dv = lambda v$.
    $endgroup$
    – xbh
    Nov 29 '18 at 8:39










  • $begingroup$
    @xbh So, my eigenvectors here would be what, exactly? This isn't obvious to me.
    $endgroup$
    – Kosta
    Nov 29 '18 at 8:47










  • $begingroup$
    Instead what did you mean by "eigenvectors of the following equation"? Usually we talk about eigenvectors of matrices, operators.
    $endgroup$
    – xbh
    Nov 29 '18 at 9:01
















0












$begingroup$


I'm a bit stuck in solving for the eigenvectors of the following equation.
begin{align}
begin{bmatrix}
2m+M-2komega & 0
\
0 & dfrac{1}{12}Ml^2 + dfrac{1}{2}ml^2 - dfrac{k}{2}l^2omega
end{bmatrix}
begin{bmatrix}
a_1 \ a_2
end{bmatrix}
=0
end{align}



I found the eigenvalues using Mathematica, but finding the Eigenvectors was problematic, so I attempted it by hand. The eigenvalues are:
begin{align}
omega_1=dfrac{3m}{2k} , omega_2 = dfrac{6m+M}{6k}
end{align}



In solving for the eigenvector corresponding to $omega_1$, I get to the following equation.



begin{align}
begin{bmatrix}
M-m & 0
\
0 & dfrac{1}{12}Ml^2 - dfrac{1}{6}ml^2
end{bmatrix}
begin{bmatrix}
a_1 \ a_2
end{bmatrix}
=0
end{align}



I'm totally unsure on how to solve this for the eigenvector. Essentially, my confusion lies in both $a_1$ and $a_2$ equal to zero here, since there are no off-diagonal terms.



Any help would be appreciated, thank you.










share|cite|improve this question









$endgroup$








  • 4




    $begingroup$
    If $$ D = begin{bmatrix} a & 0 \ 0 & bend{bmatrix},$$ then clearly $[1,0]^T, [0,1]^T$ are eigenvectors belong to $a,b$ respectively.
    $endgroup$
    – xbh
    Nov 29 '18 at 8:36










  • $begingroup$
    @xbh Can you explain this in further detail?
    $endgroup$
    – Kosta
    Nov 29 '18 at 8:37










  • $begingroup$
    That claim is pretty obvious by verifying the definition $Dv = lambda v$.
    $endgroup$
    – xbh
    Nov 29 '18 at 8:39










  • $begingroup$
    @xbh So, my eigenvectors here would be what, exactly? This isn't obvious to me.
    $endgroup$
    – Kosta
    Nov 29 '18 at 8:47










  • $begingroup$
    Instead what did you mean by "eigenvectors of the following equation"? Usually we talk about eigenvectors of matrices, operators.
    $endgroup$
    – xbh
    Nov 29 '18 at 9:01














0












0








0





$begingroup$


I'm a bit stuck in solving for the eigenvectors of the following equation.
begin{align}
begin{bmatrix}
2m+M-2komega & 0
\
0 & dfrac{1}{12}Ml^2 + dfrac{1}{2}ml^2 - dfrac{k}{2}l^2omega
end{bmatrix}
begin{bmatrix}
a_1 \ a_2
end{bmatrix}
=0
end{align}



I found the eigenvalues using Mathematica, but finding the Eigenvectors was problematic, so I attempted it by hand. The eigenvalues are:
begin{align}
omega_1=dfrac{3m}{2k} , omega_2 = dfrac{6m+M}{6k}
end{align}



In solving for the eigenvector corresponding to $omega_1$, I get to the following equation.



begin{align}
begin{bmatrix}
M-m & 0
\
0 & dfrac{1}{12}Ml^2 - dfrac{1}{6}ml^2
end{bmatrix}
begin{bmatrix}
a_1 \ a_2
end{bmatrix}
=0
end{align}



I'm totally unsure on how to solve this for the eigenvector. Essentially, my confusion lies in both $a_1$ and $a_2$ equal to zero here, since there are no off-diagonal terms.



Any help would be appreciated, thank you.










share|cite|improve this question









$endgroup$




I'm a bit stuck in solving for the eigenvectors of the following equation.
begin{align}
begin{bmatrix}
2m+M-2komega & 0
\
0 & dfrac{1}{12}Ml^2 + dfrac{1}{2}ml^2 - dfrac{k}{2}l^2omega
end{bmatrix}
begin{bmatrix}
a_1 \ a_2
end{bmatrix}
=0
end{align}



I found the eigenvalues using Mathematica, but finding the Eigenvectors was problematic, so I attempted it by hand. The eigenvalues are:
begin{align}
omega_1=dfrac{3m}{2k} , omega_2 = dfrac{6m+M}{6k}
end{align}



In solving for the eigenvector corresponding to $omega_1$, I get to the following equation.



begin{align}
begin{bmatrix}
M-m & 0
\
0 & dfrac{1}{12}Ml^2 - dfrac{1}{6}ml^2
end{bmatrix}
begin{bmatrix}
a_1 \ a_2
end{bmatrix}
=0
end{align}



I'm totally unsure on how to solve this for the eigenvector. Essentially, my confusion lies in both $a_1$ and $a_2$ equal to zero here, since there are no off-diagonal terms.



Any help would be appreciated, thank you.







linear-algebra eigenvalues-eigenvectors classical-mechanics






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share|cite|improve this question











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asked Nov 29 '18 at 8:31









KostaKosta

4991516




4991516








  • 4




    $begingroup$
    If $$ D = begin{bmatrix} a & 0 \ 0 & bend{bmatrix},$$ then clearly $[1,0]^T, [0,1]^T$ are eigenvectors belong to $a,b$ respectively.
    $endgroup$
    – xbh
    Nov 29 '18 at 8:36










  • $begingroup$
    @xbh Can you explain this in further detail?
    $endgroup$
    – Kosta
    Nov 29 '18 at 8:37










  • $begingroup$
    That claim is pretty obvious by verifying the definition $Dv = lambda v$.
    $endgroup$
    – xbh
    Nov 29 '18 at 8:39










  • $begingroup$
    @xbh So, my eigenvectors here would be what, exactly? This isn't obvious to me.
    $endgroup$
    – Kosta
    Nov 29 '18 at 8:47










  • $begingroup$
    Instead what did you mean by "eigenvectors of the following equation"? Usually we talk about eigenvectors of matrices, operators.
    $endgroup$
    – xbh
    Nov 29 '18 at 9:01














  • 4




    $begingroup$
    If $$ D = begin{bmatrix} a & 0 \ 0 & bend{bmatrix},$$ then clearly $[1,0]^T, [0,1]^T$ are eigenvectors belong to $a,b$ respectively.
    $endgroup$
    – xbh
    Nov 29 '18 at 8:36










  • $begingroup$
    @xbh Can you explain this in further detail?
    $endgroup$
    – Kosta
    Nov 29 '18 at 8:37










  • $begingroup$
    That claim is pretty obvious by verifying the definition $Dv = lambda v$.
    $endgroup$
    – xbh
    Nov 29 '18 at 8:39










  • $begingroup$
    @xbh So, my eigenvectors here would be what, exactly? This isn't obvious to me.
    $endgroup$
    – Kosta
    Nov 29 '18 at 8:47










  • $begingroup$
    Instead what did you mean by "eigenvectors of the following equation"? Usually we talk about eigenvectors of matrices, operators.
    $endgroup$
    – xbh
    Nov 29 '18 at 9:01








4




4




$begingroup$
If $$ D = begin{bmatrix} a & 0 \ 0 & bend{bmatrix},$$ then clearly $[1,0]^T, [0,1]^T$ are eigenvectors belong to $a,b$ respectively.
$endgroup$
– xbh
Nov 29 '18 at 8:36




$begingroup$
If $$ D = begin{bmatrix} a & 0 \ 0 & bend{bmatrix},$$ then clearly $[1,0]^T, [0,1]^T$ are eigenvectors belong to $a,b$ respectively.
$endgroup$
– xbh
Nov 29 '18 at 8:36












$begingroup$
@xbh Can you explain this in further detail?
$endgroup$
– Kosta
Nov 29 '18 at 8:37




$begingroup$
@xbh Can you explain this in further detail?
$endgroup$
– Kosta
Nov 29 '18 at 8:37












$begingroup$
That claim is pretty obvious by verifying the definition $Dv = lambda v$.
$endgroup$
– xbh
Nov 29 '18 at 8:39




$begingroup$
That claim is pretty obvious by verifying the definition $Dv = lambda v$.
$endgroup$
– xbh
Nov 29 '18 at 8:39












$begingroup$
@xbh So, my eigenvectors here would be what, exactly? This isn't obvious to me.
$endgroup$
– Kosta
Nov 29 '18 at 8:47




$begingroup$
@xbh So, my eigenvectors here would be what, exactly? This isn't obvious to me.
$endgroup$
– Kosta
Nov 29 '18 at 8:47












$begingroup$
Instead what did you mean by "eigenvectors of the following equation"? Usually we talk about eigenvectors of matrices, operators.
$endgroup$
– xbh
Nov 29 '18 at 9:01




$begingroup$
Instead what did you mean by "eigenvectors of the following equation"? Usually we talk about eigenvectors of matrices, operators.
$endgroup$
– xbh
Nov 29 '18 at 9:01










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