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What does this matrix mean?


Rotating Matrix by $180$ degrees through another matrixResult of multiplying a scaling matrix with a rotation matrixWhat does it mean for $AA^T$ to be symmetric?What does “if the rightmost column of the augmented matrix contains a pivot then the system has no solutions” mean?What is the meaning of subtracting from the identity matrix?What does $u^T$ mean? How to compute this?What does the superscript $t$ in this matrix addition problem mean?Simplify this matrix exponentialHow to find the basis of this matrix?What does calculating the inverse of a matrix mean?






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}







2












$begingroup$


$$
begin{bmatrix}
A\
aI
end{bmatrix}
$$



$a$ is some number is $I$ is the identity matrix. What does it mean when $A$ is on top of $aI$? What would be the resulting form?










share|cite|improve this question









$endgroup$








  • 3




    $begingroup$
    It is a concatenation of matrices. It is formed by two matrices, one below the other. The number of columns of both need to be the same. The number of rows can be different.
    $endgroup$
    – Dunkel
    8 hours ago


















2












$begingroup$


$$
begin{bmatrix}
A\
aI
end{bmatrix}
$$



$a$ is some number is $I$ is the identity matrix. What does it mean when $A$ is on top of $aI$? What would be the resulting form?










share|cite|improve this question









$endgroup$








  • 3




    $begingroup$
    It is a concatenation of matrices. It is formed by two matrices, one below the other. The number of columns of both need to be the same. The number of rows can be different.
    $endgroup$
    – Dunkel
    8 hours ago














2












2








2





$begingroup$


$$
begin{bmatrix}
A\
aI
end{bmatrix}
$$



$a$ is some number is $I$ is the identity matrix. What does it mean when $A$ is on top of $aI$? What would be the resulting form?










share|cite|improve this question









$endgroup$




$$
begin{bmatrix}
A\
aI
end{bmatrix}
$$



$a$ is some number is $I$ is the identity matrix. What does it mean when $A$ is on top of $aI$? What would be the resulting form?







linear-algebra






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked 8 hours ago









Joshua LeungJoshua Leung

2032 silver badges8 bronze badges




2032 silver badges8 bronze badges








  • 3




    $begingroup$
    It is a concatenation of matrices. It is formed by two matrices, one below the other. The number of columns of both need to be the same. The number of rows can be different.
    $endgroup$
    – Dunkel
    8 hours ago














  • 3




    $begingroup$
    It is a concatenation of matrices. It is formed by two matrices, one below the other. The number of columns of both need to be the same. The number of rows can be different.
    $endgroup$
    – Dunkel
    8 hours ago








3




3




$begingroup$
It is a concatenation of matrices. It is formed by two matrices, one below the other. The number of columns of both need to be the same. The number of rows can be different.
$endgroup$
– Dunkel
8 hours ago




$begingroup$
It is a concatenation of matrices. It is formed by two matrices, one below the other. The number of columns of both need to be the same. The number of rows can be different.
$endgroup$
– Dunkel
8 hours ago










2 Answers
2






active

oldest

votes


















4












$begingroup$

That is an example of a block matrix. Let me give you an example. Consider for example the matrix $$A = begin{pmatrix}
1 & 2 \
3 & 4
end{pmatrix} .$$
Then we get $$begin{pmatrix}
A \
aI_2
end{pmatrix} = begin{pmatrix}
1 & 2 \
3 & 4 \
a & 0 \
0 & a
end{pmatrix}.$$






share|cite|improve this answer











$endgroup$













  • $begingroup$
    That's pretty funny how we chose the same $A$ matrix for our example.
    $endgroup$
    – Dave
    8 hours ago










  • $begingroup$
    Indeed! Very canonical matrix haha.
    $endgroup$
    – ThorWittich
    8 hours ago



















2












$begingroup$

Just as Dunkel says in their comment, it represents a matrix concatenation. For example, if $$A=begin{bmatrix}1&2\3&4end{bmatrix}$$ and $a=5$ then we have $$begin{bmatrix}A\aIend{bmatrix}=begin{bmatrix}1&2\3&4\5&0\0&5end{bmatrix}$$ where I am using the $2times 2$ identity matrix.






share|cite|improve this answer









$endgroup$
















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    2 Answers
    2






    active

    oldest

    votes








    2 Answers
    2






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes









    4












    $begingroup$

    That is an example of a block matrix. Let me give you an example. Consider for example the matrix $$A = begin{pmatrix}
    1 & 2 \
    3 & 4
    end{pmatrix} .$$
    Then we get $$begin{pmatrix}
    A \
    aI_2
    end{pmatrix} = begin{pmatrix}
    1 & 2 \
    3 & 4 \
    a & 0 \
    0 & a
    end{pmatrix}.$$






    share|cite|improve this answer











    $endgroup$













    • $begingroup$
      That's pretty funny how we chose the same $A$ matrix for our example.
      $endgroup$
      – Dave
      8 hours ago










    • $begingroup$
      Indeed! Very canonical matrix haha.
      $endgroup$
      – ThorWittich
      8 hours ago
















    4












    $begingroup$

    That is an example of a block matrix. Let me give you an example. Consider for example the matrix $$A = begin{pmatrix}
    1 & 2 \
    3 & 4
    end{pmatrix} .$$
    Then we get $$begin{pmatrix}
    A \
    aI_2
    end{pmatrix} = begin{pmatrix}
    1 & 2 \
    3 & 4 \
    a & 0 \
    0 & a
    end{pmatrix}.$$






    share|cite|improve this answer











    $endgroup$













    • $begingroup$
      That's pretty funny how we chose the same $A$ matrix for our example.
      $endgroup$
      – Dave
      8 hours ago










    • $begingroup$
      Indeed! Very canonical matrix haha.
      $endgroup$
      – ThorWittich
      8 hours ago














    4












    4








    4





    $begingroup$

    That is an example of a block matrix. Let me give you an example. Consider for example the matrix $$A = begin{pmatrix}
    1 & 2 \
    3 & 4
    end{pmatrix} .$$
    Then we get $$begin{pmatrix}
    A \
    aI_2
    end{pmatrix} = begin{pmatrix}
    1 & 2 \
    3 & 4 \
    a & 0 \
    0 & a
    end{pmatrix}.$$






    share|cite|improve this answer











    $endgroup$



    That is an example of a block matrix. Let me give you an example. Consider for example the matrix $$A = begin{pmatrix}
    1 & 2 \
    3 & 4
    end{pmatrix} .$$
    Then we get $$begin{pmatrix}
    A \
    aI_2
    end{pmatrix} = begin{pmatrix}
    1 & 2 \
    3 & 4 \
    a & 0 \
    0 & a
    end{pmatrix}.$$







    share|cite|improve this answer














    share|cite|improve this answer



    share|cite|improve this answer








    edited 8 hours ago

























    answered 8 hours ago









    ThorWittichThorWittich

    2,7092 silver badges17 bronze badges




    2,7092 silver badges17 bronze badges












    • $begingroup$
      That's pretty funny how we chose the same $A$ matrix for our example.
      $endgroup$
      – Dave
      8 hours ago










    • $begingroup$
      Indeed! Very canonical matrix haha.
      $endgroup$
      – ThorWittich
      8 hours ago


















    • $begingroup$
      That's pretty funny how we chose the same $A$ matrix for our example.
      $endgroup$
      – Dave
      8 hours ago










    • $begingroup$
      Indeed! Very canonical matrix haha.
      $endgroup$
      – ThorWittich
      8 hours ago
















    $begingroup$
    That's pretty funny how we chose the same $A$ matrix for our example.
    $endgroup$
    – Dave
    8 hours ago




    $begingroup$
    That's pretty funny how we chose the same $A$ matrix for our example.
    $endgroup$
    – Dave
    8 hours ago












    $begingroup$
    Indeed! Very canonical matrix haha.
    $endgroup$
    – ThorWittich
    8 hours ago




    $begingroup$
    Indeed! Very canonical matrix haha.
    $endgroup$
    – ThorWittich
    8 hours ago













    2












    $begingroup$

    Just as Dunkel says in their comment, it represents a matrix concatenation. For example, if $$A=begin{bmatrix}1&2\3&4end{bmatrix}$$ and $a=5$ then we have $$begin{bmatrix}A\aIend{bmatrix}=begin{bmatrix}1&2\3&4\5&0\0&5end{bmatrix}$$ where I am using the $2times 2$ identity matrix.






    share|cite|improve this answer









    $endgroup$


















      2












      $begingroup$

      Just as Dunkel says in their comment, it represents a matrix concatenation. For example, if $$A=begin{bmatrix}1&2\3&4end{bmatrix}$$ and $a=5$ then we have $$begin{bmatrix}A\aIend{bmatrix}=begin{bmatrix}1&2\3&4\5&0\0&5end{bmatrix}$$ where I am using the $2times 2$ identity matrix.






      share|cite|improve this answer









      $endgroup$
















        2












        2








        2





        $begingroup$

        Just as Dunkel says in their comment, it represents a matrix concatenation. For example, if $$A=begin{bmatrix}1&2\3&4end{bmatrix}$$ and $a=5$ then we have $$begin{bmatrix}A\aIend{bmatrix}=begin{bmatrix}1&2\3&4\5&0\0&5end{bmatrix}$$ where I am using the $2times 2$ identity matrix.






        share|cite|improve this answer









        $endgroup$



        Just as Dunkel says in their comment, it represents a matrix concatenation. For example, if $$A=begin{bmatrix}1&2\3&4end{bmatrix}$$ and $a=5$ then we have $$begin{bmatrix}A\aIend{bmatrix}=begin{bmatrix}1&2\3&4\5&0\0&5end{bmatrix}$$ where I am using the $2times 2$ identity matrix.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered 8 hours ago









        DaveDave

        9,6921 gold badge11 silver badges33 bronze badges




        9,6921 gold badge11 silver badges33 bronze badges






























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