What is the “determinant” of two vectors?
$begingroup$
I came across the notation $det(v,w)$ where $v$ and $w$ are vectors. Specifically, it was about the curvature of a plane curve:
$$kappa (t) = frac{det(gamma'(t), gamma''(t)) }{|gamma'(t)|^3}$$
What is it supposed to mean?
linear-algebra differential-geometry notation determinant
$endgroup$
add a comment |
$begingroup$
I came across the notation $det(v,w)$ where $v$ and $w$ are vectors. Specifically, it was about the curvature of a plane curve:
$$kappa (t) = frac{det(gamma'(t), gamma''(t)) }{|gamma'(t)|^3}$$
What is it supposed to mean?
linear-algebra differential-geometry notation determinant
$endgroup$
$begingroup$
Are they 2D vectors? You may want to see this section of the Wikipedia article on Curvature. As you should be able to see from there, $color{blue}{det(v,w)}$ means $color{blue}{det begin{pmatrix} v_1 & w_1 \ v_2 & w_2end{pmatrix}}$.
$endgroup$
– Minus One-Twelfth
5 hours ago
$begingroup$
@MinusOne-Twelfth yes
$endgroup$
– user
5 hours ago
$begingroup$
That is the determinant of their components.
$endgroup$
– Bernard
5 hours ago
add a comment |
$begingroup$
I came across the notation $det(v,w)$ where $v$ and $w$ are vectors. Specifically, it was about the curvature of a plane curve:
$$kappa (t) = frac{det(gamma'(t), gamma''(t)) }{|gamma'(t)|^3}$$
What is it supposed to mean?
linear-algebra differential-geometry notation determinant
$endgroup$
I came across the notation $det(v,w)$ where $v$ and $w$ are vectors. Specifically, it was about the curvature of a plane curve:
$$kappa (t) = frac{det(gamma'(t), gamma''(t)) }{|gamma'(t)|^3}$$
What is it supposed to mean?
linear-algebra differential-geometry notation determinant
linear-algebra differential-geometry notation determinant
asked 5 hours ago
useruser
613
613
$begingroup$
Are they 2D vectors? You may want to see this section of the Wikipedia article on Curvature. As you should be able to see from there, $color{blue}{det(v,w)}$ means $color{blue}{det begin{pmatrix} v_1 & w_1 \ v_2 & w_2end{pmatrix}}$.
$endgroup$
– Minus One-Twelfth
5 hours ago
$begingroup$
@MinusOne-Twelfth yes
$endgroup$
– user
5 hours ago
$begingroup$
That is the determinant of their components.
$endgroup$
– Bernard
5 hours ago
add a comment |
$begingroup$
Are they 2D vectors? You may want to see this section of the Wikipedia article on Curvature. As you should be able to see from there, $color{blue}{det(v,w)}$ means $color{blue}{det begin{pmatrix} v_1 & w_1 \ v_2 & w_2end{pmatrix}}$.
$endgroup$
– Minus One-Twelfth
5 hours ago
$begingroup$
@MinusOne-Twelfth yes
$endgroup$
– user
5 hours ago
$begingroup$
That is the determinant of their components.
$endgroup$
– Bernard
5 hours ago
$begingroup$
Are they 2D vectors? You may want to see this section of the Wikipedia article on Curvature. As you should be able to see from there, $color{blue}{det(v,w)}$ means $color{blue}{det begin{pmatrix} v_1 & w_1 \ v_2 & w_2end{pmatrix}}$.
$endgroup$
– Minus One-Twelfth
5 hours ago
$begingroup$
Are they 2D vectors? You may want to see this section of the Wikipedia article on Curvature. As you should be able to see from there, $color{blue}{det(v,w)}$ means $color{blue}{det begin{pmatrix} v_1 & w_1 \ v_2 & w_2end{pmatrix}}$.
$endgroup$
– Minus One-Twelfth
5 hours ago
$begingroup$
@MinusOne-Twelfth yes
$endgroup$
– user
5 hours ago
$begingroup$
@MinusOne-Twelfth yes
$endgroup$
– user
5 hours ago
$begingroup$
That is the determinant of their components.
$endgroup$
– Bernard
5 hours ago
$begingroup$
That is the determinant of their components.
$endgroup$
– Bernard
5 hours ago
add a comment |
3 Answers
3
active
oldest
votes
$begingroup$
They formed a matrix by stacking $gamma'(t)$ and $gamma''(t)$ next to each other as column vectors. You can also regard it as the cross product of the two vectors if you extend both with a $z=0$ coordinate and take the z component of the resulting vector (that way you can relate it to the 3d formula in a way).
$endgroup$
add a comment |
$begingroup$
In general, the determinant of $n$ vectors $v_1$, $v_2$, $dots$, $v_n$ in $mathbb R^n$ is the determinant of the matrix whose columns are $v_1$, $dots$, $v_n$ (in that order).
Seen as an application whose inputs are vectors, the determinant has nice properties:
multilinear, that is linear in each variable:
$$det(v_1,dots, a v_j+b w_j,dots,v_n)
=
a det(v_1,dots, v_j,dots,v_n)
+ bdet(v_1,dots, w_j,dots,v_n)$$alternating: switching two vectors transforms the determinant in its opposite
$$det(v_1,dots, v_i, dots, v_j,dots,v_n) = det(v_1,dots, v_j, dots, v_i,dots,v_n)$$
- The value on the canonical basis $(e_1,dots,e_n)$ of $mathbb R^n$ is $1$.
$$det(e_1,dots,e_n) = 1 $$
Actually, it can be proved that the determinant is the unique alternating multilinear form whose value on the canonical basis is $1$. Many (most?) Linear Algebra books use this as a definition of the determinant (before extending the definition to matrices and then linear applications). I think it is equivalent but more satisfying than introducing the determinant by the strange "expansion along a row" formula most PreCalculus textbook use.
$endgroup$
2
$begingroup$
I believe the issue here was not that he didn't know the definition of determinant, but rather the fact that he had a determinant of two vectors rather than a matrix.
$endgroup$
– lightxbulb
3 hours ago
add a comment |
$begingroup$
Sometimes determinant of $n$ by $n$ matrix is defined as an alternating $n$-linear form; it assigns a number to each $n$-tuple of vectors $(v_1,v_2,cdots, v_n)$ following the axioms that
- For each $i=1,2,cdots, n$, the map $v_imapsto det(v_1,cdots,v_i,cdots, v_n)$ is linear.
$det(v_1,cdots,v_i,cdots,v_j,cdots,v_n)=-det(v_1,cdots,v_j,cdots,v_i,cdots,v_n)$ for each $ine j$
$det(e_1,e_2,cdots,e_n)=1$ where $(e_i)_{i=1}^n$ is the standard basis.
Following this notation, we have that
$$begin{align*}
det(v,w)&=det(v_1e_1+v_2e_2,w_1e_1+w_2e_2)
\=&v_1w_1det(e_1,e_1)+v_1w_2det(e_1,e_2)\&+v_2w_1det(e_2,e_1)+v_2w_2det(e_2,e_2)\=&v_1w_2det(e_1,e_2)-v_2w_1det(e_1,e_2)\=&v_1w_2-v_2w_1\=&left|begin{array}{cc}v_1 &w_1\v_2&w_2end{array}right|,
end{align*}$$ so it is not different from the determinant of the matrix $left[begin{array}{cc}v_1 &w_1\v_2&w_2end{array}right]$ formed by letting $v,w$ as its columns.
$endgroup$
add a comment |
Your Answer
StackExchange.ifUsing("editor", function () {
return StackExchange.using("mathjaxEditing", function () {
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
});
});
}, "mathjax-editing");
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "69"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3141770%2fwhat-is-the-determinant-of-two-vectors%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
They formed a matrix by stacking $gamma'(t)$ and $gamma''(t)$ next to each other as column vectors. You can also regard it as the cross product of the two vectors if you extend both with a $z=0$ coordinate and take the z component of the resulting vector (that way you can relate it to the 3d formula in a way).
$endgroup$
add a comment |
$begingroup$
They formed a matrix by stacking $gamma'(t)$ and $gamma''(t)$ next to each other as column vectors. You can also regard it as the cross product of the two vectors if you extend both with a $z=0$ coordinate and take the z component of the resulting vector (that way you can relate it to the 3d formula in a way).
$endgroup$
add a comment |
$begingroup$
They formed a matrix by stacking $gamma'(t)$ and $gamma''(t)$ next to each other as column vectors. You can also regard it as the cross product of the two vectors if you extend both with a $z=0$ coordinate and take the z component of the resulting vector (that way you can relate it to the 3d formula in a way).
$endgroup$
They formed a matrix by stacking $gamma'(t)$ and $gamma''(t)$ next to each other as column vectors. You can also regard it as the cross product of the two vectors if you extend both with a $z=0$ coordinate and take the z component of the resulting vector (that way you can relate it to the 3d formula in a way).
answered 5 hours ago
lightxbulblightxbulb
1,115311
1,115311
add a comment |
add a comment |
$begingroup$
In general, the determinant of $n$ vectors $v_1$, $v_2$, $dots$, $v_n$ in $mathbb R^n$ is the determinant of the matrix whose columns are $v_1$, $dots$, $v_n$ (in that order).
Seen as an application whose inputs are vectors, the determinant has nice properties:
multilinear, that is linear in each variable:
$$det(v_1,dots, a v_j+b w_j,dots,v_n)
=
a det(v_1,dots, v_j,dots,v_n)
+ bdet(v_1,dots, w_j,dots,v_n)$$alternating: switching two vectors transforms the determinant in its opposite
$$det(v_1,dots, v_i, dots, v_j,dots,v_n) = det(v_1,dots, v_j, dots, v_i,dots,v_n)$$
- The value on the canonical basis $(e_1,dots,e_n)$ of $mathbb R^n$ is $1$.
$$det(e_1,dots,e_n) = 1 $$
Actually, it can be proved that the determinant is the unique alternating multilinear form whose value on the canonical basis is $1$. Many (most?) Linear Algebra books use this as a definition of the determinant (before extending the definition to matrices and then linear applications). I think it is equivalent but more satisfying than introducing the determinant by the strange "expansion along a row" formula most PreCalculus textbook use.
$endgroup$
2
$begingroup$
I believe the issue here was not that he didn't know the definition of determinant, but rather the fact that he had a determinant of two vectors rather than a matrix.
$endgroup$
– lightxbulb
3 hours ago
add a comment |
$begingroup$
In general, the determinant of $n$ vectors $v_1$, $v_2$, $dots$, $v_n$ in $mathbb R^n$ is the determinant of the matrix whose columns are $v_1$, $dots$, $v_n$ (in that order).
Seen as an application whose inputs are vectors, the determinant has nice properties:
multilinear, that is linear in each variable:
$$det(v_1,dots, a v_j+b w_j,dots,v_n)
=
a det(v_1,dots, v_j,dots,v_n)
+ bdet(v_1,dots, w_j,dots,v_n)$$alternating: switching two vectors transforms the determinant in its opposite
$$det(v_1,dots, v_i, dots, v_j,dots,v_n) = det(v_1,dots, v_j, dots, v_i,dots,v_n)$$
- The value on the canonical basis $(e_1,dots,e_n)$ of $mathbb R^n$ is $1$.
$$det(e_1,dots,e_n) = 1 $$
Actually, it can be proved that the determinant is the unique alternating multilinear form whose value on the canonical basis is $1$. Many (most?) Linear Algebra books use this as a definition of the determinant (before extending the definition to matrices and then linear applications). I think it is equivalent but more satisfying than introducing the determinant by the strange "expansion along a row" formula most PreCalculus textbook use.
$endgroup$
2
$begingroup$
I believe the issue here was not that he didn't know the definition of determinant, but rather the fact that he had a determinant of two vectors rather than a matrix.
$endgroup$
– lightxbulb
3 hours ago
add a comment |
$begingroup$
In general, the determinant of $n$ vectors $v_1$, $v_2$, $dots$, $v_n$ in $mathbb R^n$ is the determinant of the matrix whose columns are $v_1$, $dots$, $v_n$ (in that order).
Seen as an application whose inputs are vectors, the determinant has nice properties:
multilinear, that is linear in each variable:
$$det(v_1,dots, a v_j+b w_j,dots,v_n)
=
a det(v_1,dots, v_j,dots,v_n)
+ bdet(v_1,dots, w_j,dots,v_n)$$alternating: switching two vectors transforms the determinant in its opposite
$$det(v_1,dots, v_i, dots, v_j,dots,v_n) = det(v_1,dots, v_j, dots, v_i,dots,v_n)$$
- The value on the canonical basis $(e_1,dots,e_n)$ of $mathbb R^n$ is $1$.
$$det(e_1,dots,e_n) = 1 $$
Actually, it can be proved that the determinant is the unique alternating multilinear form whose value on the canonical basis is $1$. Many (most?) Linear Algebra books use this as a definition of the determinant (before extending the definition to matrices and then linear applications). I think it is equivalent but more satisfying than introducing the determinant by the strange "expansion along a row" formula most PreCalculus textbook use.
$endgroup$
In general, the determinant of $n$ vectors $v_1$, $v_2$, $dots$, $v_n$ in $mathbb R^n$ is the determinant of the matrix whose columns are $v_1$, $dots$, $v_n$ (in that order).
Seen as an application whose inputs are vectors, the determinant has nice properties:
multilinear, that is linear in each variable:
$$det(v_1,dots, a v_j+b w_j,dots,v_n)
=
a det(v_1,dots, v_j,dots,v_n)
+ bdet(v_1,dots, w_j,dots,v_n)$$alternating: switching two vectors transforms the determinant in its opposite
$$det(v_1,dots, v_i, dots, v_j,dots,v_n) = det(v_1,dots, v_j, dots, v_i,dots,v_n)$$
- The value on the canonical basis $(e_1,dots,e_n)$ of $mathbb R^n$ is $1$.
$$det(e_1,dots,e_n) = 1 $$
Actually, it can be proved that the determinant is the unique alternating multilinear form whose value on the canonical basis is $1$. Many (most?) Linear Algebra books use this as a definition of the determinant (before extending the definition to matrices and then linear applications). I think it is equivalent but more satisfying than introducing the determinant by the strange "expansion along a row" formula most PreCalculus textbook use.
answered 4 hours ago
TaladrisTaladris
4,92431933
4,92431933
2
$begingroup$
I believe the issue here was not that he didn't know the definition of determinant, but rather the fact that he had a determinant of two vectors rather than a matrix.
$endgroup$
– lightxbulb
3 hours ago
add a comment |
2
$begingroup$
I believe the issue here was not that he didn't know the definition of determinant, but rather the fact that he had a determinant of two vectors rather than a matrix.
$endgroup$
– lightxbulb
3 hours ago
2
2
$begingroup$
I believe the issue here was not that he didn't know the definition of determinant, but rather the fact that he had a determinant of two vectors rather than a matrix.
$endgroup$
– lightxbulb
3 hours ago
$begingroup$
I believe the issue here was not that he didn't know the definition of determinant, but rather the fact that he had a determinant of two vectors rather than a matrix.
$endgroup$
– lightxbulb
3 hours ago
add a comment |
$begingroup$
Sometimes determinant of $n$ by $n$ matrix is defined as an alternating $n$-linear form; it assigns a number to each $n$-tuple of vectors $(v_1,v_2,cdots, v_n)$ following the axioms that
- For each $i=1,2,cdots, n$, the map $v_imapsto det(v_1,cdots,v_i,cdots, v_n)$ is linear.
$det(v_1,cdots,v_i,cdots,v_j,cdots,v_n)=-det(v_1,cdots,v_j,cdots,v_i,cdots,v_n)$ for each $ine j$
$det(e_1,e_2,cdots,e_n)=1$ where $(e_i)_{i=1}^n$ is the standard basis.
Following this notation, we have that
$$begin{align*}
det(v,w)&=det(v_1e_1+v_2e_2,w_1e_1+w_2e_2)
\=&v_1w_1det(e_1,e_1)+v_1w_2det(e_1,e_2)\&+v_2w_1det(e_2,e_1)+v_2w_2det(e_2,e_2)\=&v_1w_2det(e_1,e_2)-v_2w_1det(e_1,e_2)\=&v_1w_2-v_2w_1\=&left|begin{array}{cc}v_1 &w_1\v_2&w_2end{array}right|,
end{align*}$$ so it is not different from the determinant of the matrix $left[begin{array}{cc}v_1 &w_1\v_2&w_2end{array}right]$ formed by letting $v,w$ as its columns.
$endgroup$
add a comment |
$begingroup$
Sometimes determinant of $n$ by $n$ matrix is defined as an alternating $n$-linear form; it assigns a number to each $n$-tuple of vectors $(v_1,v_2,cdots, v_n)$ following the axioms that
- For each $i=1,2,cdots, n$, the map $v_imapsto det(v_1,cdots,v_i,cdots, v_n)$ is linear.
$det(v_1,cdots,v_i,cdots,v_j,cdots,v_n)=-det(v_1,cdots,v_j,cdots,v_i,cdots,v_n)$ for each $ine j$
$det(e_1,e_2,cdots,e_n)=1$ where $(e_i)_{i=1}^n$ is the standard basis.
Following this notation, we have that
$$begin{align*}
det(v,w)&=det(v_1e_1+v_2e_2,w_1e_1+w_2e_2)
\=&v_1w_1det(e_1,e_1)+v_1w_2det(e_1,e_2)\&+v_2w_1det(e_2,e_1)+v_2w_2det(e_2,e_2)\=&v_1w_2det(e_1,e_2)-v_2w_1det(e_1,e_2)\=&v_1w_2-v_2w_1\=&left|begin{array}{cc}v_1 &w_1\v_2&w_2end{array}right|,
end{align*}$$ so it is not different from the determinant of the matrix $left[begin{array}{cc}v_1 &w_1\v_2&w_2end{array}right]$ formed by letting $v,w$ as its columns.
$endgroup$
add a comment |
$begingroup$
Sometimes determinant of $n$ by $n$ matrix is defined as an alternating $n$-linear form; it assigns a number to each $n$-tuple of vectors $(v_1,v_2,cdots, v_n)$ following the axioms that
- For each $i=1,2,cdots, n$, the map $v_imapsto det(v_1,cdots,v_i,cdots, v_n)$ is linear.
$det(v_1,cdots,v_i,cdots,v_j,cdots,v_n)=-det(v_1,cdots,v_j,cdots,v_i,cdots,v_n)$ for each $ine j$
$det(e_1,e_2,cdots,e_n)=1$ where $(e_i)_{i=1}^n$ is the standard basis.
Following this notation, we have that
$$begin{align*}
det(v,w)&=det(v_1e_1+v_2e_2,w_1e_1+w_2e_2)
\=&v_1w_1det(e_1,e_1)+v_1w_2det(e_1,e_2)\&+v_2w_1det(e_2,e_1)+v_2w_2det(e_2,e_2)\=&v_1w_2det(e_1,e_2)-v_2w_1det(e_1,e_2)\=&v_1w_2-v_2w_1\=&left|begin{array}{cc}v_1 &w_1\v_2&w_2end{array}right|,
end{align*}$$ so it is not different from the determinant of the matrix $left[begin{array}{cc}v_1 &w_1\v_2&w_2end{array}right]$ formed by letting $v,w$ as its columns.
$endgroup$
Sometimes determinant of $n$ by $n$ matrix is defined as an alternating $n$-linear form; it assigns a number to each $n$-tuple of vectors $(v_1,v_2,cdots, v_n)$ following the axioms that
- For each $i=1,2,cdots, n$, the map $v_imapsto det(v_1,cdots,v_i,cdots, v_n)$ is linear.
$det(v_1,cdots,v_i,cdots,v_j,cdots,v_n)=-det(v_1,cdots,v_j,cdots,v_i,cdots,v_n)$ for each $ine j$
$det(e_1,e_2,cdots,e_n)=1$ where $(e_i)_{i=1}^n$ is the standard basis.
Following this notation, we have that
$$begin{align*}
det(v,w)&=det(v_1e_1+v_2e_2,w_1e_1+w_2e_2)
\=&v_1w_1det(e_1,e_1)+v_1w_2det(e_1,e_2)\&+v_2w_1det(e_2,e_1)+v_2w_2det(e_2,e_2)\=&v_1w_2det(e_1,e_2)-v_2w_1det(e_1,e_2)\=&v_1w_2-v_2w_1\=&left|begin{array}{cc}v_1 &w_1\v_2&w_2end{array}right|,
end{align*}$$ so it is not different from the determinant of the matrix $left[begin{array}{cc}v_1 &w_1\v_2&w_2end{array}right]$ formed by letting $v,w$ as its columns.
answered 2 mins ago
SongSong
16.8k21145
16.8k21145
add a comment |
add a comment |
Thanks for contributing an answer to Mathematics Stack Exchange!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
Use MathJax to format equations. MathJax reference.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3141770%2fwhat-is-the-determinant-of-two-vectors%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
$begingroup$
Are they 2D vectors? You may want to see this section of the Wikipedia article on Curvature. As you should be able to see from there, $color{blue}{det(v,w)}$ means $color{blue}{det begin{pmatrix} v_1 & w_1 \ v_2 & w_2end{pmatrix}}$.
$endgroup$
– Minus One-Twelfth
5 hours ago
$begingroup$
@MinusOne-Twelfth yes
$endgroup$
– user
5 hours ago
$begingroup$
That is the determinant of their components.
$endgroup$
– Bernard
5 hours ago