Find the matrix of $T$ with respect to standard basis of $V$.
$begingroup$
Let $T:Vto V$ be the rotation by an angle $theta$ counterclockwise in the plane passing through the origin perpendicular to $(1,2,3)$ where $V=Bbb R^3$
Find the matrix of $T$ with respect to standard basis of $V$.
I know that the equation of the plane passing through the origin perpendicular to $(1,2,3)$ is $x+2y+3z=0$ but I dont know how to find the matrix .
I really dont understand where does $T$ map the vector $(1,0,0)$ .
Can someone kindly help me?
Hints will suffice.I dont see any way out
linear-algebra geometry linear-transformations
$endgroup$
add a comment |
$begingroup$
Let $T:Vto V$ be the rotation by an angle $theta$ counterclockwise in the plane passing through the origin perpendicular to $(1,2,3)$ where $V=Bbb R^3$
Find the matrix of $T$ with respect to standard basis of $V$.
I know that the equation of the plane passing through the origin perpendicular to $(1,2,3)$ is $x+2y+3z=0$ but I dont know how to find the matrix .
I really dont understand where does $T$ map the vector $(1,0,0)$ .
Can someone kindly help me?
Hints will suffice.I dont see any way out
linear-algebra geometry linear-transformations
$endgroup$
add a comment |
$begingroup$
Let $T:Vto V$ be the rotation by an angle $theta$ counterclockwise in the plane passing through the origin perpendicular to $(1,2,3)$ where $V=Bbb R^3$
Find the matrix of $T$ with respect to standard basis of $V$.
I know that the equation of the plane passing through the origin perpendicular to $(1,2,3)$ is $x+2y+3z=0$ but I dont know how to find the matrix .
I really dont understand where does $T$ map the vector $(1,0,0)$ .
Can someone kindly help me?
Hints will suffice.I dont see any way out
linear-algebra geometry linear-transformations
$endgroup$
Let $T:Vto V$ be the rotation by an angle $theta$ counterclockwise in the plane passing through the origin perpendicular to $(1,2,3)$ where $V=Bbb R^3$
Find the matrix of $T$ with respect to standard basis of $V$.
I know that the equation of the plane passing through the origin perpendicular to $(1,2,3)$ is $x+2y+3z=0$ but I dont know how to find the matrix .
I really dont understand where does $T$ map the vector $(1,0,0)$ .
Can someone kindly help me?
Hints will suffice.I dont see any way out
linear-algebra geometry linear-transformations
linear-algebra geometry linear-transformations
asked Dec 6 '18 at 9:38
Join_PhDJoin_PhD
4018
4018
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
$begingroup$
Extend $v_1=frac{1}{sqrt{14}} (1,2,3)$ to an orthonormal basis $B=(v_1, v_2, v_3)$. Write down the matrix of $T$ with respect to this basis. Perform a change of basis to the standard basis $S=(e_1, e_2, e_3)$.
The vector $v_1$ I picked is a vector in the direction $(1,2,3)$ having length $|v_1|=1$. To extend this to an orthonormal basis, you can proceed in (at least) two ways:
- extend to any basis first, e.g. $v_1, e_1, e_2$ and apply Gram–Schmidt orhonormalization
- find one unit vector $v_2$ orthogonal to $v_1$ and then compute the cross product $v_3=v_1times v_2$.
Having done that, we can find the matrix of $T$ with respect to $B=(v_1, v_2, v_3)$.
Since $v_1$ is a vector along the axis of rotation, we have $T(v_1)=v_1$. The vectors $v_2,v_3$ form an orthonormal basis of the plane perpendicular to $v_1$, so they get rotated by $theta$ in this plane and we have
begin{align*}
T(v_2) &= cos(theta), v_2 + sin(theta), v_3, \
T(v_2) &= -sin(theta), v_2 + cos(theta), v_3.
end{align*}
Thus, the matrix of $T$ with respect to the basis $B$ is given by
$$M(T)_B = begin{bmatrix} 1 & 0&0\0 &cos theta&-sin theta\0& sintheta &costhetaend{bmatrix}.$$
The change of base matrix from $v_1,v_2,v_3$ to the standard basis is the matrix $C_{S,B}=(v_1 ,|, v_2 ,|, v_3)$ with columns $v_1, v_2, v_3$.
Hence, the matrix of $T$ with respect to the standard basis is
$$
M(T)_S = C_{S,B} ,M(T)_B ,C_{B,S} = C_{S,B} ,M(T)_B ,C_{S,B}^{-1}.
$$
$endgroup$
$begingroup$
But T is the rotation about this plane,I dont understand why should I follow the above procedure to find its matrix
$endgroup$
– Join_PhD
Dec 6 '18 at 10:08
$begingroup$
Can you please give some details using geometry
$endgroup$
– Join_PhD
Dec 6 '18 at 10:08
$begingroup$
Do you know how to write down a rotation about the axis $(1,0,0)$ by an angle $theta$?
$endgroup$
– Christoph
Dec 6 '18 at 10:09
$begingroup$
Yes it is $begin{bmatrix} 1 & 0&0\0 &cos theta&-sin theta\0& sintheta &costhetaend{bmatrix}$
$endgroup$
– Join_PhD
Dec 6 '18 at 10:10
$begingroup$
This is the matrix of $T$ with respect to $v_1, v_2, v_3$. Now perform a change of basis.
$endgroup$
– Christoph
Dec 6 '18 at 10:12
|
show 10 more comments
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%2f3028271%2ffind-the-matrix-of-t-with-respect-to-standard-basis-of-v%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
Extend $v_1=frac{1}{sqrt{14}} (1,2,3)$ to an orthonormal basis $B=(v_1, v_2, v_3)$. Write down the matrix of $T$ with respect to this basis. Perform a change of basis to the standard basis $S=(e_1, e_2, e_3)$.
The vector $v_1$ I picked is a vector in the direction $(1,2,3)$ having length $|v_1|=1$. To extend this to an orthonormal basis, you can proceed in (at least) two ways:
- extend to any basis first, e.g. $v_1, e_1, e_2$ and apply Gram–Schmidt orhonormalization
- find one unit vector $v_2$ orthogonal to $v_1$ and then compute the cross product $v_3=v_1times v_2$.
Having done that, we can find the matrix of $T$ with respect to $B=(v_1, v_2, v_3)$.
Since $v_1$ is a vector along the axis of rotation, we have $T(v_1)=v_1$. The vectors $v_2,v_3$ form an orthonormal basis of the plane perpendicular to $v_1$, so they get rotated by $theta$ in this plane and we have
begin{align*}
T(v_2) &= cos(theta), v_2 + sin(theta), v_3, \
T(v_2) &= -sin(theta), v_2 + cos(theta), v_3.
end{align*}
Thus, the matrix of $T$ with respect to the basis $B$ is given by
$$M(T)_B = begin{bmatrix} 1 & 0&0\0 &cos theta&-sin theta\0& sintheta &costhetaend{bmatrix}.$$
The change of base matrix from $v_1,v_2,v_3$ to the standard basis is the matrix $C_{S,B}=(v_1 ,|, v_2 ,|, v_3)$ with columns $v_1, v_2, v_3$.
Hence, the matrix of $T$ with respect to the standard basis is
$$
M(T)_S = C_{S,B} ,M(T)_B ,C_{B,S} = C_{S,B} ,M(T)_B ,C_{S,B}^{-1}.
$$
$endgroup$
$begingroup$
But T is the rotation about this plane,I dont understand why should I follow the above procedure to find its matrix
$endgroup$
– Join_PhD
Dec 6 '18 at 10:08
$begingroup$
Can you please give some details using geometry
$endgroup$
– Join_PhD
Dec 6 '18 at 10:08
$begingroup$
Do you know how to write down a rotation about the axis $(1,0,0)$ by an angle $theta$?
$endgroup$
– Christoph
Dec 6 '18 at 10:09
$begingroup$
Yes it is $begin{bmatrix} 1 & 0&0\0 &cos theta&-sin theta\0& sintheta &costhetaend{bmatrix}$
$endgroup$
– Join_PhD
Dec 6 '18 at 10:10
$begingroup$
This is the matrix of $T$ with respect to $v_1, v_2, v_3$. Now perform a change of basis.
$endgroup$
– Christoph
Dec 6 '18 at 10:12
|
show 10 more comments
$begingroup$
Extend $v_1=frac{1}{sqrt{14}} (1,2,3)$ to an orthonormal basis $B=(v_1, v_2, v_3)$. Write down the matrix of $T$ with respect to this basis. Perform a change of basis to the standard basis $S=(e_1, e_2, e_3)$.
The vector $v_1$ I picked is a vector in the direction $(1,2,3)$ having length $|v_1|=1$. To extend this to an orthonormal basis, you can proceed in (at least) two ways:
- extend to any basis first, e.g. $v_1, e_1, e_2$ and apply Gram–Schmidt orhonormalization
- find one unit vector $v_2$ orthogonal to $v_1$ and then compute the cross product $v_3=v_1times v_2$.
Having done that, we can find the matrix of $T$ with respect to $B=(v_1, v_2, v_3)$.
Since $v_1$ is a vector along the axis of rotation, we have $T(v_1)=v_1$. The vectors $v_2,v_3$ form an orthonormal basis of the plane perpendicular to $v_1$, so they get rotated by $theta$ in this plane and we have
begin{align*}
T(v_2) &= cos(theta), v_2 + sin(theta), v_3, \
T(v_2) &= -sin(theta), v_2 + cos(theta), v_3.
end{align*}
Thus, the matrix of $T$ with respect to the basis $B$ is given by
$$M(T)_B = begin{bmatrix} 1 & 0&0\0 &cos theta&-sin theta\0& sintheta &costhetaend{bmatrix}.$$
The change of base matrix from $v_1,v_2,v_3$ to the standard basis is the matrix $C_{S,B}=(v_1 ,|, v_2 ,|, v_3)$ with columns $v_1, v_2, v_3$.
Hence, the matrix of $T$ with respect to the standard basis is
$$
M(T)_S = C_{S,B} ,M(T)_B ,C_{B,S} = C_{S,B} ,M(T)_B ,C_{S,B}^{-1}.
$$
$endgroup$
$begingroup$
But T is the rotation about this plane,I dont understand why should I follow the above procedure to find its matrix
$endgroup$
– Join_PhD
Dec 6 '18 at 10:08
$begingroup$
Can you please give some details using geometry
$endgroup$
– Join_PhD
Dec 6 '18 at 10:08
$begingroup$
Do you know how to write down a rotation about the axis $(1,0,0)$ by an angle $theta$?
$endgroup$
– Christoph
Dec 6 '18 at 10:09
$begingroup$
Yes it is $begin{bmatrix} 1 & 0&0\0 &cos theta&-sin theta\0& sintheta &costhetaend{bmatrix}$
$endgroup$
– Join_PhD
Dec 6 '18 at 10:10
$begingroup$
This is the matrix of $T$ with respect to $v_1, v_2, v_3$. Now perform a change of basis.
$endgroup$
– Christoph
Dec 6 '18 at 10:12
|
show 10 more comments
$begingroup$
Extend $v_1=frac{1}{sqrt{14}} (1,2,3)$ to an orthonormal basis $B=(v_1, v_2, v_3)$. Write down the matrix of $T$ with respect to this basis. Perform a change of basis to the standard basis $S=(e_1, e_2, e_3)$.
The vector $v_1$ I picked is a vector in the direction $(1,2,3)$ having length $|v_1|=1$. To extend this to an orthonormal basis, you can proceed in (at least) two ways:
- extend to any basis first, e.g. $v_1, e_1, e_2$ and apply Gram–Schmidt orhonormalization
- find one unit vector $v_2$ orthogonal to $v_1$ and then compute the cross product $v_3=v_1times v_2$.
Having done that, we can find the matrix of $T$ with respect to $B=(v_1, v_2, v_3)$.
Since $v_1$ is a vector along the axis of rotation, we have $T(v_1)=v_1$. The vectors $v_2,v_3$ form an orthonormal basis of the plane perpendicular to $v_1$, so they get rotated by $theta$ in this plane and we have
begin{align*}
T(v_2) &= cos(theta), v_2 + sin(theta), v_3, \
T(v_2) &= -sin(theta), v_2 + cos(theta), v_3.
end{align*}
Thus, the matrix of $T$ with respect to the basis $B$ is given by
$$M(T)_B = begin{bmatrix} 1 & 0&0\0 &cos theta&-sin theta\0& sintheta &costhetaend{bmatrix}.$$
The change of base matrix from $v_1,v_2,v_3$ to the standard basis is the matrix $C_{S,B}=(v_1 ,|, v_2 ,|, v_3)$ with columns $v_1, v_2, v_3$.
Hence, the matrix of $T$ with respect to the standard basis is
$$
M(T)_S = C_{S,B} ,M(T)_B ,C_{B,S} = C_{S,B} ,M(T)_B ,C_{S,B}^{-1}.
$$
$endgroup$
Extend $v_1=frac{1}{sqrt{14}} (1,2,3)$ to an orthonormal basis $B=(v_1, v_2, v_3)$. Write down the matrix of $T$ with respect to this basis. Perform a change of basis to the standard basis $S=(e_1, e_2, e_3)$.
The vector $v_1$ I picked is a vector in the direction $(1,2,3)$ having length $|v_1|=1$. To extend this to an orthonormal basis, you can proceed in (at least) two ways:
- extend to any basis first, e.g. $v_1, e_1, e_2$ and apply Gram–Schmidt orhonormalization
- find one unit vector $v_2$ orthogonal to $v_1$ and then compute the cross product $v_3=v_1times v_2$.
Having done that, we can find the matrix of $T$ with respect to $B=(v_1, v_2, v_3)$.
Since $v_1$ is a vector along the axis of rotation, we have $T(v_1)=v_1$. The vectors $v_2,v_3$ form an orthonormal basis of the plane perpendicular to $v_1$, so they get rotated by $theta$ in this plane and we have
begin{align*}
T(v_2) &= cos(theta), v_2 + sin(theta), v_3, \
T(v_2) &= -sin(theta), v_2 + cos(theta), v_3.
end{align*}
Thus, the matrix of $T$ with respect to the basis $B$ is given by
$$M(T)_B = begin{bmatrix} 1 & 0&0\0 &cos theta&-sin theta\0& sintheta &costhetaend{bmatrix}.$$
The change of base matrix from $v_1,v_2,v_3$ to the standard basis is the matrix $C_{S,B}=(v_1 ,|, v_2 ,|, v_3)$ with columns $v_1, v_2, v_3$.
Hence, the matrix of $T$ with respect to the standard basis is
$$
M(T)_S = C_{S,B} ,M(T)_B ,C_{B,S} = C_{S,B} ,M(T)_B ,C_{S,B}^{-1}.
$$
edited Dec 6 '18 at 10:35
answered Dec 6 '18 at 9:46
ChristophChristoph
12k1642
12k1642
$begingroup$
But T is the rotation about this plane,I dont understand why should I follow the above procedure to find its matrix
$endgroup$
– Join_PhD
Dec 6 '18 at 10:08
$begingroup$
Can you please give some details using geometry
$endgroup$
– Join_PhD
Dec 6 '18 at 10:08
$begingroup$
Do you know how to write down a rotation about the axis $(1,0,0)$ by an angle $theta$?
$endgroup$
– Christoph
Dec 6 '18 at 10:09
$begingroup$
Yes it is $begin{bmatrix} 1 & 0&0\0 &cos theta&-sin theta\0& sintheta &costhetaend{bmatrix}$
$endgroup$
– Join_PhD
Dec 6 '18 at 10:10
$begingroup$
This is the matrix of $T$ with respect to $v_1, v_2, v_3$. Now perform a change of basis.
$endgroup$
– Christoph
Dec 6 '18 at 10:12
|
show 10 more comments
$begingroup$
But T is the rotation about this plane,I dont understand why should I follow the above procedure to find its matrix
$endgroup$
– Join_PhD
Dec 6 '18 at 10:08
$begingroup$
Can you please give some details using geometry
$endgroup$
– Join_PhD
Dec 6 '18 at 10:08
$begingroup$
Do you know how to write down a rotation about the axis $(1,0,0)$ by an angle $theta$?
$endgroup$
– Christoph
Dec 6 '18 at 10:09
$begingroup$
Yes it is $begin{bmatrix} 1 & 0&0\0 &cos theta&-sin theta\0& sintheta &costhetaend{bmatrix}$
$endgroup$
– Join_PhD
Dec 6 '18 at 10:10
$begingroup$
This is the matrix of $T$ with respect to $v_1, v_2, v_3$. Now perform a change of basis.
$endgroup$
– Christoph
Dec 6 '18 at 10:12
$begingroup$
But T is the rotation about this plane,I dont understand why should I follow the above procedure to find its matrix
$endgroup$
– Join_PhD
Dec 6 '18 at 10:08
$begingroup$
But T is the rotation about this plane,I dont understand why should I follow the above procedure to find its matrix
$endgroup$
– Join_PhD
Dec 6 '18 at 10:08
$begingroup$
Can you please give some details using geometry
$endgroup$
– Join_PhD
Dec 6 '18 at 10:08
$begingroup$
Can you please give some details using geometry
$endgroup$
– Join_PhD
Dec 6 '18 at 10:08
$begingroup$
Do you know how to write down a rotation about the axis $(1,0,0)$ by an angle $theta$?
$endgroup$
– Christoph
Dec 6 '18 at 10:09
$begingroup$
Do you know how to write down a rotation about the axis $(1,0,0)$ by an angle $theta$?
$endgroup$
– Christoph
Dec 6 '18 at 10:09
$begingroup$
Yes it is $begin{bmatrix} 1 & 0&0\0 &cos theta&-sin theta\0& sintheta &costhetaend{bmatrix}$
$endgroup$
– Join_PhD
Dec 6 '18 at 10:10
$begingroup$
Yes it is $begin{bmatrix} 1 & 0&0\0 &cos theta&-sin theta\0& sintheta &costhetaend{bmatrix}$
$endgroup$
– Join_PhD
Dec 6 '18 at 10:10
$begingroup$
This is the matrix of $T$ with respect to $v_1, v_2, v_3$. Now perform a change of basis.
$endgroup$
– Christoph
Dec 6 '18 at 10:12
$begingroup$
This is the matrix of $T$ with respect to $v_1, v_2, v_3$. Now perform a change of basis.
$endgroup$
– Christoph
Dec 6 '18 at 10:12
|
show 10 more comments
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%2f3028271%2ffind-the-matrix-of-t-with-respect-to-standard-basis-of-v%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