How to know if $mathrmIm A = mathbb R^n$ given a matrix? The Next CEO of Stack Overflow$ker A capmathrmIm A = 0 Rightarrow ker A + mathrmIm A = R^n$.Given a linear map $T:Vto V$, is it true that $V=ker(T) oplus mathrmim(T)$?The space spanned by the rows of the Kernel matrix.Linear map and its matrixDetermining if $defrkoperatornamerankrk(A)$ is always equivalent to $rk(A^t*A)$Can we say something about the rows of the null space matrixlinear algebra: image, kernel and transpose$n - mathrmrank, A ge mathrmrank, A - mathrmrank, A^2$Find the farthest rotation matrix in $mathrmSO(3)$ from a given matrix.Existence of a subspace of the domain of a linear map with specific properties

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How to know if $mathrmIm A = mathbb R^n$ given a matrix?



The Next CEO of Stack Overflow$ker A capmathrmIm A = 0 Rightarrow ker A + mathrmIm A = R^n$.Given a linear map $T:Vto V$, is it true that $V=ker(T) oplus mathrmim(T)$?The space spanned by the rows of the Kernel matrix.Linear map and its matrixDetermining if $defrkoperatornamerankrk(A)$ is always equivalent to $rk(A^t*A)$Can we say something about the rows of the null space matrixlinear algebra: image, kernel and transpose$n - mathrmrank, A ge mathrmrank, A - mathrmrank, A^2$Find the farthest rotation matrix in $mathrmSO(3)$ from a given matrix.Existence of a subspace of the domain of a linear map with specific properties










2












$begingroup$


Knowing that I have $5times 6$ matrix $A$ with $dim mathrmIm, A = 4$ and $dim ker A= 2$, I am asked if $mathrmIm ,A = mathbb R^4$? The answer is that $mathrmIm, A$ is a subspace of $mathbb R^5$. Is it because we have 5 rows? If not why?










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New contributor




Dr.Stone is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.







$endgroup$







  • 1




    $begingroup$
    Yes, we have 5 rows and six columns. Therefore, $A$ as a linear mapping maps from $mathbb R^6$ to $mathbb R^5$. Hence, $Im(A)$ is a subspace of $mathbb R^5$. The space $mathbb R^4$ is another object and not a subspace of $mathbb R^5$. It can be embedded though, but the result will not be $mathbb R^4$ anymore.
    $endgroup$
    – amsmath
    Mar 28 at 0:54















2












$begingroup$


Knowing that I have $5times 6$ matrix $A$ with $dim mathrmIm, A = 4$ and $dim ker A= 2$, I am asked if $mathrmIm ,A = mathbb R^4$? The answer is that $mathrmIm, A$ is a subspace of $mathbb R^5$. Is it because we have 5 rows? If not why?










share|cite|improve this question









New contributor




Dr.Stone is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.







$endgroup$







  • 1




    $begingroup$
    Yes, we have 5 rows and six columns. Therefore, $A$ as a linear mapping maps from $mathbb R^6$ to $mathbb R^5$. Hence, $Im(A)$ is a subspace of $mathbb R^5$. The space $mathbb R^4$ is another object and not a subspace of $mathbb R^5$. It can be embedded though, but the result will not be $mathbb R^4$ anymore.
    $endgroup$
    – amsmath
    Mar 28 at 0:54













2












2








2





$begingroup$


Knowing that I have $5times 6$ matrix $A$ with $dim mathrmIm, A = 4$ and $dim ker A= 2$, I am asked if $mathrmIm ,A = mathbb R^4$? The answer is that $mathrmIm, A$ is a subspace of $mathbb R^5$. Is it because we have 5 rows? If not why?










share|cite|improve this question









New contributor




Dr.Stone is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.







$endgroup$




Knowing that I have $5times 6$ matrix $A$ with $dim mathrmIm, A = 4$ and $dim ker A= 2$, I am asked if $mathrmIm ,A = mathbb R^4$? The answer is that $mathrmIm, A$ is a subspace of $mathbb R^5$. Is it because we have 5 rows? If not why?







linear-algebra






share|cite|improve this question









New contributor




Dr.Stone is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











share|cite|improve this question









New contributor




Dr.Stone is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.









share|cite|improve this question




share|cite|improve this question








edited Mar 28 at 1:07









Brian

1,208116




1,208116






New contributor




Dr.Stone is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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asked Mar 28 at 0:46









Dr.StoneDr.Stone

335




335




New contributor




Dr.Stone is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.





New contributor





Dr.Stone is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.






Dr.Stone is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.







  • 1




    $begingroup$
    Yes, we have 5 rows and six columns. Therefore, $A$ as a linear mapping maps from $mathbb R^6$ to $mathbb R^5$. Hence, $Im(A)$ is a subspace of $mathbb R^5$. The space $mathbb R^4$ is another object and not a subspace of $mathbb R^5$. It can be embedded though, but the result will not be $mathbb R^4$ anymore.
    $endgroup$
    – amsmath
    Mar 28 at 0:54












  • 1




    $begingroup$
    Yes, we have 5 rows and six columns. Therefore, $A$ as a linear mapping maps from $mathbb R^6$ to $mathbb R^5$. Hence, $Im(A)$ is a subspace of $mathbb R^5$. The space $mathbb R^4$ is another object and not a subspace of $mathbb R^5$. It can be embedded though, but the result will not be $mathbb R^4$ anymore.
    $endgroup$
    – amsmath
    Mar 28 at 0:54







1




1




$begingroup$
Yes, we have 5 rows and six columns. Therefore, $A$ as a linear mapping maps from $mathbb R^6$ to $mathbb R^5$. Hence, $Im(A)$ is a subspace of $mathbb R^5$. The space $mathbb R^4$ is another object and not a subspace of $mathbb R^5$. It can be embedded though, but the result will not be $mathbb R^4$ anymore.
$endgroup$
– amsmath
Mar 28 at 0:54




$begingroup$
Yes, we have 5 rows and six columns. Therefore, $A$ as a linear mapping maps from $mathbb R^6$ to $mathbb R^5$. Hence, $Im(A)$ is a subspace of $mathbb R^5$. The space $mathbb R^4$ is another object and not a subspace of $mathbb R^5$. It can be embedded though, but the result will not be $mathbb R^4$ anymore.
$endgroup$
– amsmath
Mar 28 at 0:54










1 Answer
1






active

oldest

votes


















1












$begingroup$

Any $mtimes n$ matrix can be thought of as describing a linear transformation from $mathbb R^n$ to $mathbb R^m$. The fact that $A$ is a $5 times 6$ matrix tells us that its column space (or, image) will be a subspace of $mathbb R^5$. Since $dim mathrmIm, A = 4$, we know that this subspace has dimension four, but this is not the same as $mathbb R^4$.



Consider the the following subspace of $mathbb R^3$:



$$
V=mathrmspan, left beginbmatrix1\1\0endbmatrix, beginbmatrix0\1\1endbmatrixright
$$



It is easy to see that the subspace $V$ is a plane situated in $mathbb R^3$. However, this plane is clearly not the same as $mathbb R^2$; it is a separate object altogether. The same is true for the column space of your matrix. Though it has four dimensions, it is not the "four-dimensional space," but rather a subsection of "five-dimensional space."






share|cite|improve this answer











$endgroup$












  • $begingroup$
    "Though it is four dimensional, it is not the whole of "four-dimensional space"" -- I think this is misleading...
    $endgroup$
    – amsmath
    Mar 28 at 1:31











  • $begingroup$
    @amsmath How so? Is there a way that this could be better expressed?
    $endgroup$
    – Brian
    Mar 28 at 1:35










  • $begingroup$
    "Not a whole of" somehow indicates that it is a part of four-dimensional space, which is of course not true. Rather the contrary. It is a "whole" four-dimensional space. But just not $mathbb R^4$. ;o)
    $endgroup$
    – amsmath
    Mar 28 at 1:38










  • $begingroup$
    @amsmath I see your point, though I feel that my phrasing adequately conveys that sentiment, especially with the surrounding context. Nonetheless, I have edited my post to remove any possible ambiguity for future readers. Thanks for your close review!
    $endgroup$
    – Brian
    Mar 28 at 1:49










  • $begingroup$
    The thing is that you can very easily confuse people that are not really safe with maths because they are often insecured.
    $endgroup$
    – amsmath
    Mar 28 at 1:55












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1 Answer
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active

oldest

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1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









1












$begingroup$

Any $mtimes n$ matrix can be thought of as describing a linear transformation from $mathbb R^n$ to $mathbb R^m$. The fact that $A$ is a $5 times 6$ matrix tells us that its column space (or, image) will be a subspace of $mathbb R^5$. Since $dim mathrmIm, A = 4$, we know that this subspace has dimension four, but this is not the same as $mathbb R^4$.



Consider the the following subspace of $mathbb R^3$:



$$
V=mathrmspan, left beginbmatrix1\1\0endbmatrix, beginbmatrix0\1\1endbmatrixright
$$



It is easy to see that the subspace $V$ is a plane situated in $mathbb R^3$. However, this plane is clearly not the same as $mathbb R^2$; it is a separate object altogether. The same is true for the column space of your matrix. Though it has four dimensions, it is not the "four-dimensional space," but rather a subsection of "five-dimensional space."






share|cite|improve this answer











$endgroup$












  • $begingroup$
    "Though it is four dimensional, it is not the whole of "four-dimensional space"" -- I think this is misleading...
    $endgroup$
    – amsmath
    Mar 28 at 1:31











  • $begingroup$
    @amsmath How so? Is there a way that this could be better expressed?
    $endgroup$
    – Brian
    Mar 28 at 1:35










  • $begingroup$
    "Not a whole of" somehow indicates that it is a part of four-dimensional space, which is of course not true. Rather the contrary. It is a "whole" four-dimensional space. But just not $mathbb R^4$. ;o)
    $endgroup$
    – amsmath
    Mar 28 at 1:38










  • $begingroup$
    @amsmath I see your point, though I feel that my phrasing adequately conveys that sentiment, especially with the surrounding context. Nonetheless, I have edited my post to remove any possible ambiguity for future readers. Thanks for your close review!
    $endgroup$
    – Brian
    Mar 28 at 1:49










  • $begingroup$
    The thing is that you can very easily confuse people that are not really safe with maths because they are often insecured.
    $endgroup$
    – amsmath
    Mar 28 at 1:55
















1












$begingroup$

Any $mtimes n$ matrix can be thought of as describing a linear transformation from $mathbb R^n$ to $mathbb R^m$. The fact that $A$ is a $5 times 6$ matrix tells us that its column space (or, image) will be a subspace of $mathbb R^5$. Since $dim mathrmIm, A = 4$, we know that this subspace has dimension four, but this is not the same as $mathbb R^4$.



Consider the the following subspace of $mathbb R^3$:



$$
V=mathrmspan, left beginbmatrix1\1\0endbmatrix, beginbmatrix0\1\1endbmatrixright
$$



It is easy to see that the subspace $V$ is a plane situated in $mathbb R^3$. However, this plane is clearly not the same as $mathbb R^2$; it is a separate object altogether. The same is true for the column space of your matrix. Though it has four dimensions, it is not the "four-dimensional space," but rather a subsection of "five-dimensional space."






share|cite|improve this answer











$endgroup$












  • $begingroup$
    "Though it is four dimensional, it is not the whole of "four-dimensional space"" -- I think this is misleading...
    $endgroup$
    – amsmath
    Mar 28 at 1:31











  • $begingroup$
    @amsmath How so? Is there a way that this could be better expressed?
    $endgroup$
    – Brian
    Mar 28 at 1:35










  • $begingroup$
    "Not a whole of" somehow indicates that it is a part of four-dimensional space, which is of course not true. Rather the contrary. It is a "whole" four-dimensional space. But just not $mathbb R^4$. ;o)
    $endgroup$
    – amsmath
    Mar 28 at 1:38










  • $begingroup$
    @amsmath I see your point, though I feel that my phrasing adequately conveys that sentiment, especially with the surrounding context. Nonetheless, I have edited my post to remove any possible ambiguity for future readers. Thanks for your close review!
    $endgroup$
    – Brian
    Mar 28 at 1:49










  • $begingroup$
    The thing is that you can very easily confuse people that are not really safe with maths because they are often insecured.
    $endgroup$
    – amsmath
    Mar 28 at 1:55














1












1








1





$begingroup$

Any $mtimes n$ matrix can be thought of as describing a linear transformation from $mathbb R^n$ to $mathbb R^m$. The fact that $A$ is a $5 times 6$ matrix tells us that its column space (or, image) will be a subspace of $mathbb R^5$. Since $dim mathrmIm, A = 4$, we know that this subspace has dimension four, but this is not the same as $mathbb R^4$.



Consider the the following subspace of $mathbb R^3$:



$$
V=mathrmspan, left beginbmatrix1\1\0endbmatrix, beginbmatrix0\1\1endbmatrixright
$$



It is easy to see that the subspace $V$ is a plane situated in $mathbb R^3$. However, this plane is clearly not the same as $mathbb R^2$; it is a separate object altogether. The same is true for the column space of your matrix. Though it has four dimensions, it is not the "four-dimensional space," but rather a subsection of "five-dimensional space."






share|cite|improve this answer











$endgroup$



Any $mtimes n$ matrix can be thought of as describing a linear transformation from $mathbb R^n$ to $mathbb R^m$. The fact that $A$ is a $5 times 6$ matrix tells us that its column space (or, image) will be a subspace of $mathbb R^5$. Since $dim mathrmIm, A = 4$, we know that this subspace has dimension four, but this is not the same as $mathbb R^4$.



Consider the the following subspace of $mathbb R^3$:



$$
V=mathrmspan, left beginbmatrix1\1\0endbmatrix, beginbmatrix0\1\1endbmatrixright
$$



It is easy to see that the subspace $V$ is a plane situated in $mathbb R^3$. However, this plane is clearly not the same as $mathbb R^2$; it is a separate object altogether. The same is true for the column space of your matrix. Though it has four dimensions, it is not the "four-dimensional space," but rather a subsection of "five-dimensional space."







share|cite|improve this answer














share|cite|improve this answer



share|cite|improve this answer








edited Mar 28 at 1:49

























answered Mar 28 at 0:57









BrianBrian

1,208116




1,208116











  • $begingroup$
    "Though it is four dimensional, it is not the whole of "four-dimensional space"" -- I think this is misleading...
    $endgroup$
    – amsmath
    Mar 28 at 1:31











  • $begingroup$
    @amsmath How so? Is there a way that this could be better expressed?
    $endgroup$
    – Brian
    Mar 28 at 1:35










  • $begingroup$
    "Not a whole of" somehow indicates that it is a part of four-dimensional space, which is of course not true. Rather the contrary. It is a "whole" four-dimensional space. But just not $mathbb R^4$. ;o)
    $endgroup$
    – amsmath
    Mar 28 at 1:38










  • $begingroup$
    @amsmath I see your point, though I feel that my phrasing adequately conveys that sentiment, especially with the surrounding context. Nonetheless, I have edited my post to remove any possible ambiguity for future readers. Thanks for your close review!
    $endgroup$
    – Brian
    Mar 28 at 1:49










  • $begingroup$
    The thing is that you can very easily confuse people that are not really safe with maths because they are often insecured.
    $endgroup$
    – amsmath
    Mar 28 at 1:55

















  • $begingroup$
    "Though it is four dimensional, it is not the whole of "four-dimensional space"" -- I think this is misleading...
    $endgroup$
    – amsmath
    Mar 28 at 1:31











  • $begingroup$
    @amsmath How so? Is there a way that this could be better expressed?
    $endgroup$
    – Brian
    Mar 28 at 1:35










  • $begingroup$
    "Not a whole of" somehow indicates that it is a part of four-dimensional space, which is of course not true. Rather the contrary. It is a "whole" four-dimensional space. But just not $mathbb R^4$. ;o)
    $endgroup$
    – amsmath
    Mar 28 at 1:38










  • $begingroup$
    @amsmath I see your point, though I feel that my phrasing adequately conveys that sentiment, especially with the surrounding context. Nonetheless, I have edited my post to remove any possible ambiguity for future readers. Thanks for your close review!
    $endgroup$
    – Brian
    Mar 28 at 1:49










  • $begingroup$
    The thing is that you can very easily confuse people that are not really safe with maths because they are often insecured.
    $endgroup$
    – amsmath
    Mar 28 at 1:55
















$begingroup$
"Though it is four dimensional, it is not the whole of "four-dimensional space"" -- I think this is misleading...
$endgroup$
– amsmath
Mar 28 at 1:31





$begingroup$
"Though it is four dimensional, it is not the whole of "four-dimensional space"" -- I think this is misleading...
$endgroup$
– amsmath
Mar 28 at 1:31













$begingroup$
@amsmath How so? Is there a way that this could be better expressed?
$endgroup$
– Brian
Mar 28 at 1:35




$begingroup$
@amsmath How so? Is there a way that this could be better expressed?
$endgroup$
– Brian
Mar 28 at 1:35












$begingroup$
"Not a whole of" somehow indicates that it is a part of four-dimensional space, which is of course not true. Rather the contrary. It is a "whole" four-dimensional space. But just not $mathbb R^4$. ;o)
$endgroup$
– amsmath
Mar 28 at 1:38




$begingroup$
"Not a whole of" somehow indicates that it is a part of four-dimensional space, which is of course not true. Rather the contrary. It is a "whole" four-dimensional space. But just not $mathbb R^4$. ;o)
$endgroup$
– amsmath
Mar 28 at 1:38












$begingroup$
@amsmath I see your point, though I feel that my phrasing adequately conveys that sentiment, especially with the surrounding context. Nonetheless, I have edited my post to remove any possible ambiguity for future readers. Thanks for your close review!
$endgroup$
– Brian
Mar 28 at 1:49




$begingroup$
@amsmath I see your point, though I feel that my phrasing adequately conveys that sentiment, especially with the surrounding context. Nonetheless, I have edited my post to remove any possible ambiguity for future readers. Thanks for your close review!
$endgroup$
– Brian
Mar 28 at 1:49












$begingroup$
The thing is that you can very easily confuse people that are not really safe with maths because they are often insecured.
$endgroup$
– amsmath
Mar 28 at 1:55





$begingroup$
The thing is that you can very easily confuse people that are not really safe with maths because they are often insecured.
$endgroup$
– amsmath
Mar 28 at 1:55











Dr.Stone is a new contributor. Be nice, and check out our Code of Conduct.









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Dr.Stone is a new contributor. Be nice, and check out our Code of Conduct.












Dr.Stone is a new contributor. Be nice, and check out our Code of Conduct.











Dr.Stone is a new contributor. Be nice, and check out our Code of Conduct.














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