If $n$ vectors are linearly independent, is their span $mathbb{R}^n$?
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Have $n$ vectors in $mathbb{R}^n$.
If the $n$ vectors are linearly independent, can we conclude that their span is $mathbb{R}^n$?
linear-algebra geometry vectors
$endgroup$
add a comment |
$begingroup$
Have $n$ vectors in $mathbb{R}^n$.
If the $n$ vectors are linearly independent, can we conclude that their span is $mathbb{R}^n$?
linear-algebra geometry vectors
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5
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Yes${}{}{}{}{}{}$.
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– user63181
May 26 '14 at 23:00
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How do you define span? Is this a conclusion that might follow from a definition you're familiar with?
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– Muphrid
May 26 '14 at 23:01
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@Muphrid: My concept of Span is pretty basic. To me, it's just the set of all vectors resulting from all linear combinations of the $n$ vectors.
$endgroup$
– Zol Tun Kul
May 26 '14 at 23:02
add a comment |
$begingroup$
Have $n$ vectors in $mathbb{R}^n$.
If the $n$ vectors are linearly independent, can we conclude that their span is $mathbb{R}^n$?
linear-algebra geometry vectors
$endgroup$
Have $n$ vectors in $mathbb{R}^n$.
If the $n$ vectors are linearly independent, can we conclude that their span is $mathbb{R}^n$?
linear-algebra geometry vectors
linear-algebra geometry vectors
edited May 26 '14 at 23:01
Git Gud
28.9k1050101
28.9k1050101
asked May 26 '14 at 23:00
Zol Tun KulZol Tun Kul
2,84682951
2,84682951
5
$begingroup$
Yes${}{}{}{}{}{}$.
$endgroup$
– user63181
May 26 '14 at 23:00
$begingroup$
How do you define span? Is this a conclusion that might follow from a definition you're familiar with?
$endgroup$
– Muphrid
May 26 '14 at 23:01
$begingroup$
@Muphrid: My concept of Span is pretty basic. To me, it's just the set of all vectors resulting from all linear combinations of the $n$ vectors.
$endgroup$
– Zol Tun Kul
May 26 '14 at 23:02
add a comment |
5
$begingroup$
Yes${}{}{}{}{}{}$.
$endgroup$
– user63181
May 26 '14 at 23:00
$begingroup$
How do you define span? Is this a conclusion that might follow from a definition you're familiar with?
$endgroup$
– Muphrid
May 26 '14 at 23:01
$begingroup$
@Muphrid: My concept of Span is pretty basic. To me, it's just the set of all vectors resulting from all linear combinations of the $n$ vectors.
$endgroup$
– Zol Tun Kul
May 26 '14 at 23:02
5
5
$begingroup$
Yes${}{}{}{}{}{}$.
$endgroup$
– user63181
May 26 '14 at 23:00
$begingroup$
Yes${}{}{}{}{}{}$.
$endgroup$
– user63181
May 26 '14 at 23:00
$begingroup$
How do you define span? Is this a conclusion that might follow from a definition you're familiar with?
$endgroup$
– Muphrid
May 26 '14 at 23:01
$begingroup$
How do you define span? Is this a conclusion that might follow from a definition you're familiar with?
$endgroup$
– Muphrid
May 26 '14 at 23:01
$begingroup$
@Muphrid: My concept of Span is pretty basic. To me, it's just the set of all vectors resulting from all linear combinations of the $n$ vectors.
$endgroup$
– Zol Tun Kul
May 26 '14 at 23:02
$begingroup$
@Muphrid: My concept of Span is pretty basic. To me, it's just the set of all vectors resulting from all linear combinations of the $n$ vectors.
$endgroup$
– Zol Tun Kul
May 26 '14 at 23:02
add a comment |
3 Answers
3
active
oldest
votes
$begingroup$
A useful result in linear algebra is:
Proposition. Let $W$ be a subspace of a finite-dimensional vector space $V$. If $dim W=dim V$, then $W=V$.
If we are given linearly independent $v_1,dotsc,v_ninBbb R^n$, then $DeclareMathOperator{Span}{Span}Span{v_1,dotsc,v_n}$ is an $n$-dimensional subspace of $Bbb R^n$. Since $dim Bbb R^n=n$, the proposition implies that $Span{v_1,dotsc,v_n}=Bbb R^n$.
Can you prove this proposition?
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add a comment |
$begingroup$
You can use the theorem that every linearly independent set in a vector space $V$ can be extended to a basis of $V$. Since the dimension of $mathbb{R}^n$ is simply $n$, the extension of the $n$ vectors to a basis is trivial (i.e. the vectors are unchanged); these vectors therefore already span $mathbb{R}^n$.
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$begingroup$
That assumes some theorems about dimension, of course - namely, that dimension is well-defined...
$endgroup$
– Thomas Andrews
May 26 '14 at 23:22
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True, although that follows easily from the theorem that linearly independent sets are no longer than spanning sets. If $B_1$ and $B_2$ are bases of $V$, then $B_1$ can be no longer than $B_2$ and the converse is true, so their lengths must be equal.
$endgroup$
– Michael M
May 27 '14 at 1:06
add a comment |
$begingroup$
Hint: if the span of $m$ linearly independent vectors ${v_1,dots,v_m}$ is a proper subspace $U$ of $mathbb{R}^n$, then, for every vector $vinmathbb{R}$, $vnotin U$, the set ${v_1,dots,v_m,v}$ is linearly independent.
Can you see there's a contradiction if $m=n$?
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add a comment |
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3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
A useful result in linear algebra is:
Proposition. Let $W$ be a subspace of a finite-dimensional vector space $V$. If $dim W=dim V$, then $W=V$.
If we are given linearly independent $v_1,dotsc,v_ninBbb R^n$, then $DeclareMathOperator{Span}{Span}Span{v_1,dotsc,v_n}$ is an $n$-dimensional subspace of $Bbb R^n$. Since $dim Bbb R^n=n$, the proposition implies that $Span{v_1,dotsc,v_n}=Bbb R^n$.
Can you prove this proposition?
$endgroup$
add a comment |
$begingroup$
A useful result in linear algebra is:
Proposition. Let $W$ be a subspace of a finite-dimensional vector space $V$. If $dim W=dim V$, then $W=V$.
If we are given linearly independent $v_1,dotsc,v_ninBbb R^n$, then $DeclareMathOperator{Span}{Span}Span{v_1,dotsc,v_n}$ is an $n$-dimensional subspace of $Bbb R^n$. Since $dim Bbb R^n=n$, the proposition implies that $Span{v_1,dotsc,v_n}=Bbb R^n$.
Can you prove this proposition?
$endgroup$
add a comment |
$begingroup$
A useful result in linear algebra is:
Proposition. Let $W$ be a subspace of a finite-dimensional vector space $V$. If $dim W=dim V$, then $W=V$.
If we are given linearly independent $v_1,dotsc,v_ninBbb R^n$, then $DeclareMathOperator{Span}{Span}Span{v_1,dotsc,v_n}$ is an $n$-dimensional subspace of $Bbb R^n$. Since $dim Bbb R^n=n$, the proposition implies that $Span{v_1,dotsc,v_n}=Bbb R^n$.
Can you prove this proposition?
$endgroup$
A useful result in linear algebra is:
Proposition. Let $W$ be a subspace of a finite-dimensional vector space $V$. If $dim W=dim V$, then $W=V$.
If we are given linearly independent $v_1,dotsc,v_ninBbb R^n$, then $DeclareMathOperator{Span}{Span}Span{v_1,dotsc,v_n}$ is an $n$-dimensional subspace of $Bbb R^n$. Since $dim Bbb R^n=n$, the proposition implies that $Span{v_1,dotsc,v_n}=Bbb R^n$.
Can you prove this proposition?
answered May 26 '14 at 23:08
Brian FitzpatrickBrian Fitzpatrick
21.8k42959
21.8k42959
add a comment |
add a comment |
$begingroup$
You can use the theorem that every linearly independent set in a vector space $V$ can be extended to a basis of $V$. Since the dimension of $mathbb{R}^n$ is simply $n$, the extension of the $n$ vectors to a basis is trivial (i.e. the vectors are unchanged); these vectors therefore already span $mathbb{R}^n$.
$endgroup$
$begingroup$
That assumes some theorems about dimension, of course - namely, that dimension is well-defined...
$endgroup$
– Thomas Andrews
May 26 '14 at 23:22
$begingroup$
True, although that follows easily from the theorem that linearly independent sets are no longer than spanning sets. If $B_1$ and $B_2$ are bases of $V$, then $B_1$ can be no longer than $B_2$ and the converse is true, so their lengths must be equal.
$endgroup$
– Michael M
May 27 '14 at 1:06
add a comment |
$begingroup$
You can use the theorem that every linearly independent set in a vector space $V$ can be extended to a basis of $V$. Since the dimension of $mathbb{R}^n$ is simply $n$, the extension of the $n$ vectors to a basis is trivial (i.e. the vectors are unchanged); these vectors therefore already span $mathbb{R}^n$.
$endgroup$
$begingroup$
That assumes some theorems about dimension, of course - namely, that dimension is well-defined...
$endgroup$
– Thomas Andrews
May 26 '14 at 23:22
$begingroup$
True, although that follows easily from the theorem that linearly independent sets are no longer than spanning sets. If $B_1$ and $B_2$ are bases of $V$, then $B_1$ can be no longer than $B_2$ and the converse is true, so their lengths must be equal.
$endgroup$
– Michael M
May 27 '14 at 1:06
add a comment |
$begingroup$
You can use the theorem that every linearly independent set in a vector space $V$ can be extended to a basis of $V$. Since the dimension of $mathbb{R}^n$ is simply $n$, the extension of the $n$ vectors to a basis is trivial (i.e. the vectors are unchanged); these vectors therefore already span $mathbb{R}^n$.
$endgroup$
You can use the theorem that every linearly independent set in a vector space $V$ can be extended to a basis of $V$. Since the dimension of $mathbb{R}^n$ is simply $n$, the extension of the $n$ vectors to a basis is trivial (i.e. the vectors are unchanged); these vectors therefore already span $mathbb{R}^n$.
answered May 26 '14 at 23:10
Michael MMichael M
2,183614
2,183614
$begingroup$
That assumes some theorems about dimension, of course - namely, that dimension is well-defined...
$endgroup$
– Thomas Andrews
May 26 '14 at 23:22
$begingroup$
True, although that follows easily from the theorem that linearly independent sets are no longer than spanning sets. If $B_1$ and $B_2$ are bases of $V$, then $B_1$ can be no longer than $B_2$ and the converse is true, so their lengths must be equal.
$endgroup$
– Michael M
May 27 '14 at 1:06
add a comment |
$begingroup$
That assumes some theorems about dimension, of course - namely, that dimension is well-defined...
$endgroup$
– Thomas Andrews
May 26 '14 at 23:22
$begingroup$
True, although that follows easily from the theorem that linearly independent sets are no longer than spanning sets. If $B_1$ and $B_2$ are bases of $V$, then $B_1$ can be no longer than $B_2$ and the converse is true, so their lengths must be equal.
$endgroup$
– Michael M
May 27 '14 at 1:06
$begingroup$
That assumes some theorems about dimension, of course - namely, that dimension is well-defined...
$endgroup$
– Thomas Andrews
May 26 '14 at 23:22
$begingroup$
That assumes some theorems about dimension, of course - namely, that dimension is well-defined...
$endgroup$
– Thomas Andrews
May 26 '14 at 23:22
$begingroup$
True, although that follows easily from the theorem that linearly independent sets are no longer than spanning sets. If $B_1$ and $B_2$ are bases of $V$, then $B_1$ can be no longer than $B_2$ and the converse is true, so their lengths must be equal.
$endgroup$
– Michael M
May 27 '14 at 1:06
$begingroup$
True, although that follows easily from the theorem that linearly independent sets are no longer than spanning sets. If $B_1$ and $B_2$ are bases of $V$, then $B_1$ can be no longer than $B_2$ and the converse is true, so their lengths must be equal.
$endgroup$
– Michael M
May 27 '14 at 1:06
add a comment |
$begingroup$
Hint: if the span of $m$ linearly independent vectors ${v_1,dots,v_m}$ is a proper subspace $U$ of $mathbb{R}^n$, then, for every vector $vinmathbb{R}$, $vnotin U$, the set ${v_1,dots,v_m,v}$ is linearly independent.
Can you see there's a contradiction if $m=n$?
$endgroup$
add a comment |
$begingroup$
Hint: if the span of $m$ linearly independent vectors ${v_1,dots,v_m}$ is a proper subspace $U$ of $mathbb{R}^n$, then, for every vector $vinmathbb{R}$, $vnotin U$, the set ${v_1,dots,v_m,v}$ is linearly independent.
Can you see there's a contradiction if $m=n$?
$endgroup$
add a comment |
$begingroup$
Hint: if the span of $m$ linearly independent vectors ${v_1,dots,v_m}$ is a proper subspace $U$ of $mathbb{R}^n$, then, for every vector $vinmathbb{R}$, $vnotin U$, the set ${v_1,dots,v_m,v}$ is linearly independent.
Can you see there's a contradiction if $m=n$?
$endgroup$
Hint: if the span of $m$ linearly independent vectors ${v_1,dots,v_m}$ is a proper subspace $U$ of $mathbb{R}^n$, then, for every vector $vinmathbb{R}$, $vnotin U$, the set ${v_1,dots,v_m,v}$ is linearly independent.
Can you see there's a contradiction if $m=n$?
answered May 26 '14 at 23:11
egregegreg
185k1486206
185k1486206
add a comment |
add a comment |
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5
$begingroup$
Yes${}{}{}{}{}{}$.
$endgroup$
– user63181
May 26 '14 at 23:00
$begingroup$
How do you define span? Is this a conclusion that might follow from a definition you're familiar with?
$endgroup$
– Muphrid
May 26 '14 at 23:01
$begingroup$
@Muphrid: My concept of Span is pretty basic. To me, it's just the set of all vectors resulting from all linear combinations of the $n$ vectors.
$endgroup$
– Zol Tun Kul
May 26 '14 at 23:02