Using chain rule to find dz/dt leaving answer in terms of t
$begingroup$
Can anyone tell me if I have done this correctly
Using the chain rule Find $ frac{dz}{dt} $
if $ z=xy^2, x=e^{-3t} , y=-sin(2t) $
Leaving answer in terms of $t$
$ frac{dz}{dt} =frac{partial z}{partial x} cdot frac{partial x}{partial t} + frac{partial z}{partial y} cdot frac{partial y}{partial t}$
$ frac{dz}{dt} = (y^2 cdot -3e^{-3t})+(2xy cdot -2cos(2t))$
$ frac{dz}{dt} = (sin^2(2t)cdot-3e^{-3t})+(2e^{-3t}cdot-sin(2t) cdot-2cos(2t))$
Many thanks in advance
ordinary-differential-equations chain-rule
$endgroup$
add a comment |
$begingroup$
Can anyone tell me if I have done this correctly
Using the chain rule Find $ frac{dz}{dt} $
if $ z=xy^2, x=e^{-3t} , y=-sin(2t) $
Leaving answer in terms of $t$
$ frac{dz}{dt} =frac{partial z}{partial x} cdot frac{partial x}{partial t} + frac{partial z}{partial y} cdot frac{partial y}{partial t}$
$ frac{dz}{dt} = (y^2 cdot -3e^{-3t})+(2xy cdot -2cos(2t))$
$ frac{dz}{dt} = (sin^2(2t)cdot-3e^{-3t})+(2e^{-3t}cdot-sin(2t) cdot-2cos(2t))$
Many thanks in advance
ordinary-differential-equations chain-rule
$endgroup$
1
$begingroup$
Looks fine. One little critique: When writing out the chain rule for $frac{dz}{dt}$, you may want to write the derivatives of $x$ and $y$ as total derivatives rather than partial derivatives since each is a function of only $t$.
$endgroup$
– user137731
Sep 28 '16 at 1:56
$begingroup$
oh. you are absolutley correct thanks for pointing that out. That was where i was getting confused but was just me not paying attention to detail. You are a champ.
$endgroup$
– Buddy
Sep 28 '16 at 1:59
$begingroup$
Correction - should have read $ frac{dz}{dt} =frac{partial z}{partial x} cdot frac{dx}{dt} + frac{partial z}{partial y} cdot frac{dy}{dt}$
$endgroup$
– Buddy
Sep 28 '16 at 2:00
add a comment |
$begingroup$
Can anyone tell me if I have done this correctly
Using the chain rule Find $ frac{dz}{dt} $
if $ z=xy^2, x=e^{-3t} , y=-sin(2t) $
Leaving answer in terms of $t$
$ frac{dz}{dt} =frac{partial z}{partial x} cdot frac{partial x}{partial t} + frac{partial z}{partial y} cdot frac{partial y}{partial t}$
$ frac{dz}{dt} = (y^2 cdot -3e^{-3t})+(2xy cdot -2cos(2t))$
$ frac{dz}{dt} = (sin^2(2t)cdot-3e^{-3t})+(2e^{-3t}cdot-sin(2t) cdot-2cos(2t))$
Many thanks in advance
ordinary-differential-equations chain-rule
$endgroup$
Can anyone tell me if I have done this correctly
Using the chain rule Find $ frac{dz}{dt} $
if $ z=xy^2, x=e^{-3t} , y=-sin(2t) $
Leaving answer in terms of $t$
$ frac{dz}{dt} =frac{partial z}{partial x} cdot frac{partial x}{partial t} + frac{partial z}{partial y} cdot frac{partial y}{partial t}$
$ frac{dz}{dt} = (y^2 cdot -3e^{-3t})+(2xy cdot -2cos(2t))$
$ frac{dz}{dt} = (sin^2(2t)cdot-3e^{-3t})+(2e^{-3t}cdot-sin(2t) cdot-2cos(2t))$
Many thanks in advance
ordinary-differential-equations chain-rule
ordinary-differential-equations chain-rule
asked Sep 28 '16 at 1:52
BuddyBuddy
4328
4328
1
$begingroup$
Looks fine. One little critique: When writing out the chain rule for $frac{dz}{dt}$, you may want to write the derivatives of $x$ and $y$ as total derivatives rather than partial derivatives since each is a function of only $t$.
$endgroup$
– user137731
Sep 28 '16 at 1:56
$begingroup$
oh. you are absolutley correct thanks for pointing that out. That was where i was getting confused but was just me not paying attention to detail. You are a champ.
$endgroup$
– Buddy
Sep 28 '16 at 1:59
$begingroup$
Correction - should have read $ frac{dz}{dt} =frac{partial z}{partial x} cdot frac{dx}{dt} + frac{partial z}{partial y} cdot frac{dy}{dt}$
$endgroup$
– Buddy
Sep 28 '16 at 2:00
add a comment |
1
$begingroup$
Looks fine. One little critique: When writing out the chain rule for $frac{dz}{dt}$, you may want to write the derivatives of $x$ and $y$ as total derivatives rather than partial derivatives since each is a function of only $t$.
$endgroup$
– user137731
Sep 28 '16 at 1:56
$begingroup$
oh. you are absolutley correct thanks for pointing that out. That was where i was getting confused but was just me not paying attention to detail. You are a champ.
$endgroup$
– Buddy
Sep 28 '16 at 1:59
$begingroup$
Correction - should have read $ frac{dz}{dt} =frac{partial z}{partial x} cdot frac{dx}{dt} + frac{partial z}{partial y} cdot frac{dy}{dt}$
$endgroup$
– Buddy
Sep 28 '16 at 2:00
1
1
$begingroup$
Looks fine. One little critique: When writing out the chain rule for $frac{dz}{dt}$, you may want to write the derivatives of $x$ and $y$ as total derivatives rather than partial derivatives since each is a function of only $t$.
$endgroup$
– user137731
Sep 28 '16 at 1:56
$begingroup$
Looks fine. One little critique: When writing out the chain rule for $frac{dz}{dt}$, you may want to write the derivatives of $x$ and $y$ as total derivatives rather than partial derivatives since each is a function of only $t$.
$endgroup$
– user137731
Sep 28 '16 at 1:56
$begingroup$
oh. you are absolutley correct thanks for pointing that out. That was where i was getting confused but was just me not paying attention to detail. You are a champ.
$endgroup$
– Buddy
Sep 28 '16 at 1:59
$begingroup$
oh. you are absolutley correct thanks for pointing that out. That was where i was getting confused but was just me not paying attention to detail. You are a champ.
$endgroup$
– Buddy
Sep 28 '16 at 1:59
$begingroup$
Correction - should have read $ frac{dz}{dt} =frac{partial z}{partial x} cdot frac{dx}{dt} + frac{partial z}{partial y} cdot frac{dy}{dt}$
$endgroup$
– Buddy
Sep 28 '16 at 2:00
$begingroup$
Correction - should have read $ frac{dz}{dt} =frac{partial z}{partial x} cdot frac{dx}{dt} + frac{partial z}{partial y} cdot frac{dy}{dt}$
$endgroup$
– Buddy
Sep 28 '16 at 2:00
add a comment |
1 Answer
1
active
oldest
votes
$begingroup$
We need to find:
$$text{z}'(t)=frac{text{d}text{z}(t)}{text{d}t}=frac{text{d}}{text{d}t}left(e^{-3t}cdotleft(-sin(2t)right)^2right)=$$
$$frac{text{d}}{text{d}t}left(e^{-3t}sin^2(2t)right)=e^{-3t}sin(2t)left(4cos(2t)-3sin(2t)right)$$
Using:
- The product rule:
$$frac{text{d}}{text{d}t}left(f(t)cdot y(t)right)=f(t)cdotfrac{text{d}}{text{d}t}left(y(t)right)+y(t)cdotfrac{text{d}}{text{d}t}left(f(t)right)=y(t)cdot f'(t)+f(t)cdot y'(t)$$ - $$frac{text{d}}{text{d}t}left(e^{x(t)}right)=e^{x(t)}cdotfrac{text{d}}{text{d}t}left(x(t)right)=x'(t)cdot e^{x(t)}$$
- When $text{C}$ is a constant:
$$frac{text{d}}{text{d}t}left(text{C}cdot q(t)right)=text{C}cdotfrac{text{d}}{text{d}t}left(q(t)right)=text{C}cdot q'(t)$$ - When $text{n}$ is a constant, using the chain rule:
$$frac{text{d}}{text{d}t}left(w(t)^text{n}right)=text{n}cdot w(t)^{text{n}-1}cdotfrac{text{d}}{text{d}t}left(w(t)right)=text{n}cdot w(t)^{text{n}-1}cdot w'(t)$$ - When $text{m}$ is a constant, using the chain rule:
$$frac{text{d}}{text{d}t}left(v(text{m}t)right)=frac{text{d}}{text{d}t}left(text{m}tright)cdot v'(text{m}t)=text{m}cdot v'(text{m}t)$$
$endgroup$
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%2f1944393%2fusing-chain-rule-to-find-dz-dt-leaving-answer-in-terms-of-t%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
$begingroup$
We need to find:
$$text{z}'(t)=frac{text{d}text{z}(t)}{text{d}t}=frac{text{d}}{text{d}t}left(e^{-3t}cdotleft(-sin(2t)right)^2right)=$$
$$frac{text{d}}{text{d}t}left(e^{-3t}sin^2(2t)right)=e^{-3t}sin(2t)left(4cos(2t)-3sin(2t)right)$$
Using:
- The product rule:
$$frac{text{d}}{text{d}t}left(f(t)cdot y(t)right)=f(t)cdotfrac{text{d}}{text{d}t}left(y(t)right)+y(t)cdotfrac{text{d}}{text{d}t}left(f(t)right)=y(t)cdot f'(t)+f(t)cdot y'(t)$$ - $$frac{text{d}}{text{d}t}left(e^{x(t)}right)=e^{x(t)}cdotfrac{text{d}}{text{d}t}left(x(t)right)=x'(t)cdot e^{x(t)}$$
- When $text{C}$ is a constant:
$$frac{text{d}}{text{d}t}left(text{C}cdot q(t)right)=text{C}cdotfrac{text{d}}{text{d}t}left(q(t)right)=text{C}cdot q'(t)$$ - When $text{n}$ is a constant, using the chain rule:
$$frac{text{d}}{text{d}t}left(w(t)^text{n}right)=text{n}cdot w(t)^{text{n}-1}cdotfrac{text{d}}{text{d}t}left(w(t)right)=text{n}cdot w(t)^{text{n}-1}cdot w'(t)$$ - When $text{m}$ is a constant, using the chain rule:
$$frac{text{d}}{text{d}t}left(v(text{m}t)right)=frac{text{d}}{text{d}t}left(text{m}tright)cdot v'(text{m}t)=text{m}cdot v'(text{m}t)$$
$endgroup$
add a comment |
$begingroup$
We need to find:
$$text{z}'(t)=frac{text{d}text{z}(t)}{text{d}t}=frac{text{d}}{text{d}t}left(e^{-3t}cdotleft(-sin(2t)right)^2right)=$$
$$frac{text{d}}{text{d}t}left(e^{-3t}sin^2(2t)right)=e^{-3t}sin(2t)left(4cos(2t)-3sin(2t)right)$$
Using:
- The product rule:
$$frac{text{d}}{text{d}t}left(f(t)cdot y(t)right)=f(t)cdotfrac{text{d}}{text{d}t}left(y(t)right)+y(t)cdotfrac{text{d}}{text{d}t}left(f(t)right)=y(t)cdot f'(t)+f(t)cdot y'(t)$$ - $$frac{text{d}}{text{d}t}left(e^{x(t)}right)=e^{x(t)}cdotfrac{text{d}}{text{d}t}left(x(t)right)=x'(t)cdot e^{x(t)}$$
- When $text{C}$ is a constant:
$$frac{text{d}}{text{d}t}left(text{C}cdot q(t)right)=text{C}cdotfrac{text{d}}{text{d}t}left(q(t)right)=text{C}cdot q'(t)$$ - When $text{n}$ is a constant, using the chain rule:
$$frac{text{d}}{text{d}t}left(w(t)^text{n}right)=text{n}cdot w(t)^{text{n}-1}cdotfrac{text{d}}{text{d}t}left(w(t)right)=text{n}cdot w(t)^{text{n}-1}cdot w'(t)$$ - When $text{m}$ is a constant, using the chain rule:
$$frac{text{d}}{text{d}t}left(v(text{m}t)right)=frac{text{d}}{text{d}t}left(text{m}tright)cdot v'(text{m}t)=text{m}cdot v'(text{m}t)$$
$endgroup$
add a comment |
$begingroup$
We need to find:
$$text{z}'(t)=frac{text{d}text{z}(t)}{text{d}t}=frac{text{d}}{text{d}t}left(e^{-3t}cdotleft(-sin(2t)right)^2right)=$$
$$frac{text{d}}{text{d}t}left(e^{-3t}sin^2(2t)right)=e^{-3t}sin(2t)left(4cos(2t)-3sin(2t)right)$$
Using:
- The product rule:
$$frac{text{d}}{text{d}t}left(f(t)cdot y(t)right)=f(t)cdotfrac{text{d}}{text{d}t}left(y(t)right)+y(t)cdotfrac{text{d}}{text{d}t}left(f(t)right)=y(t)cdot f'(t)+f(t)cdot y'(t)$$ - $$frac{text{d}}{text{d}t}left(e^{x(t)}right)=e^{x(t)}cdotfrac{text{d}}{text{d}t}left(x(t)right)=x'(t)cdot e^{x(t)}$$
- When $text{C}$ is a constant:
$$frac{text{d}}{text{d}t}left(text{C}cdot q(t)right)=text{C}cdotfrac{text{d}}{text{d}t}left(q(t)right)=text{C}cdot q'(t)$$ - When $text{n}$ is a constant, using the chain rule:
$$frac{text{d}}{text{d}t}left(w(t)^text{n}right)=text{n}cdot w(t)^{text{n}-1}cdotfrac{text{d}}{text{d}t}left(w(t)right)=text{n}cdot w(t)^{text{n}-1}cdot w'(t)$$ - When $text{m}$ is a constant, using the chain rule:
$$frac{text{d}}{text{d}t}left(v(text{m}t)right)=frac{text{d}}{text{d}t}left(text{m}tright)cdot v'(text{m}t)=text{m}cdot v'(text{m}t)$$
$endgroup$
We need to find:
$$text{z}'(t)=frac{text{d}text{z}(t)}{text{d}t}=frac{text{d}}{text{d}t}left(e^{-3t}cdotleft(-sin(2t)right)^2right)=$$
$$frac{text{d}}{text{d}t}left(e^{-3t}sin^2(2t)right)=e^{-3t}sin(2t)left(4cos(2t)-3sin(2t)right)$$
Using:
- The product rule:
$$frac{text{d}}{text{d}t}left(f(t)cdot y(t)right)=f(t)cdotfrac{text{d}}{text{d}t}left(y(t)right)+y(t)cdotfrac{text{d}}{text{d}t}left(f(t)right)=y(t)cdot f'(t)+f(t)cdot y'(t)$$ - $$frac{text{d}}{text{d}t}left(e^{x(t)}right)=e^{x(t)}cdotfrac{text{d}}{text{d}t}left(x(t)right)=x'(t)cdot e^{x(t)}$$
- When $text{C}$ is a constant:
$$frac{text{d}}{text{d}t}left(text{C}cdot q(t)right)=text{C}cdotfrac{text{d}}{text{d}t}left(q(t)right)=text{C}cdot q'(t)$$ - When $text{n}$ is a constant, using the chain rule:
$$frac{text{d}}{text{d}t}left(w(t)^text{n}right)=text{n}cdot w(t)^{text{n}-1}cdotfrac{text{d}}{text{d}t}left(w(t)right)=text{n}cdot w(t)^{text{n}-1}cdot w'(t)$$ - When $text{m}$ is a constant, using the chain rule:
$$frac{text{d}}{text{d}t}left(v(text{m}t)right)=frac{text{d}}{text{d}t}left(text{m}tright)cdot v'(text{m}t)=text{m}cdot v'(text{m}t)$$
answered Sep 28 '16 at 19:54
JanJan
21.7k31240
21.7k31240
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%2f1944393%2fusing-chain-rule-to-find-dz-dt-leaving-answer-in-terms-of-t%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
1
$begingroup$
Looks fine. One little critique: When writing out the chain rule for $frac{dz}{dt}$, you may want to write the derivatives of $x$ and $y$ as total derivatives rather than partial derivatives since each is a function of only $t$.
$endgroup$
– user137731
Sep 28 '16 at 1:56
$begingroup$
oh. you are absolutley correct thanks for pointing that out. That was where i was getting confused but was just me not paying attention to detail. You are a champ.
$endgroup$
– Buddy
Sep 28 '16 at 1:59
$begingroup$
Correction - should have read $ frac{dz}{dt} =frac{partial z}{partial x} cdot frac{dx}{dt} + frac{partial z}{partial y} cdot frac{dy}{dt}$
$endgroup$
– Buddy
Sep 28 '16 at 2:00