Applying Chain Rule to Dimensionless Transformation











up vote
0
down vote

favorite












Hello I am trying to show that the equation



$frac{dN}{dt} = rN(1 - frac{N(t - tau)}{K})$



can be rewritten in a dimensionless form as



$frac{dy}{dx} = lambda y(1 - y(x - 1))$
using the transformations $y = frac{N}{K}$ and $x = frac{t}{tau}$.



So far my attempt at the problem is to assume $frac{dy}{dx} = frac{dy}{dN}*frac{dN}{dt}*frac{dt}{dx}$. Using the given information of $y = frac{N}{K}$ and $x = frac{t}{tau}$ it seems



$frac{dy}{dN} = frac{1}{K}$ and $frac{dx}{dt} = frac{1}{tau} Rightarrow frac{dt}{dx} = tau$



I then proceeded to substitute this information into $frac{dy}{dx} = frac{dy}{dN}*frac{dN}{dt}*frac{dt}{dx}$,



$frac{dy}{dx} = frac{1}{K}*(rN(1 - frac{N(t - tau)}{K}))*tau = rtau(frac{N}{K}(1 - frac{N}{K}(t - tau)) =$



$rtau y(1 - y(t - tau))$



At this point I am unsure if I should try to think of a factor to multiply the last step of my simplification so that I can assume $lambda$ is equal to some factor and then match it with what $frac{dy}{dx}$ is supposed to be or if I made a mistake in how I approached the problem so far and it involves a more complicated understanding of how to apply the chain rule. Needless to say in my simplification it should be noted that the inside function of $y = frac{N}{K}$ currently is in the same form of $(t - tau)$ as it is in $frac{dN}{dt}$ but by multiplying by $frac{1}{tau}$ the resultant inside will be of the form $(frac{t}{tau} - frac{tau}{tau}) = (x - 1)$. So my question is what needs to be done to further proceed along this problem? Any help would be much appreciated, thanks.










share|cite|improve this question


















  • 1




    $y = N/K$ is a little bit imprecise. More accurate is $y(x) = N(tau x)/K$. Does that help?
    – eyeballfrog
    Nov 14 at 6:47










  • @eyeballfrog So should I just distribute $tau$ in the inside function while letting $lambda = r$ to get the desired form or do I need to reassess what $frac{dy}{dN}$ should be using the more precise form of $y(x) = N(tau x)/K$?
    – Jmath99
    Nov 14 at 7:43















up vote
0
down vote

favorite












Hello I am trying to show that the equation



$frac{dN}{dt} = rN(1 - frac{N(t - tau)}{K})$



can be rewritten in a dimensionless form as



$frac{dy}{dx} = lambda y(1 - y(x - 1))$
using the transformations $y = frac{N}{K}$ and $x = frac{t}{tau}$.



So far my attempt at the problem is to assume $frac{dy}{dx} = frac{dy}{dN}*frac{dN}{dt}*frac{dt}{dx}$. Using the given information of $y = frac{N}{K}$ and $x = frac{t}{tau}$ it seems



$frac{dy}{dN} = frac{1}{K}$ and $frac{dx}{dt} = frac{1}{tau} Rightarrow frac{dt}{dx} = tau$



I then proceeded to substitute this information into $frac{dy}{dx} = frac{dy}{dN}*frac{dN}{dt}*frac{dt}{dx}$,



$frac{dy}{dx} = frac{1}{K}*(rN(1 - frac{N(t - tau)}{K}))*tau = rtau(frac{N}{K}(1 - frac{N}{K}(t - tau)) =$



$rtau y(1 - y(t - tau))$



At this point I am unsure if I should try to think of a factor to multiply the last step of my simplification so that I can assume $lambda$ is equal to some factor and then match it with what $frac{dy}{dx}$ is supposed to be or if I made a mistake in how I approached the problem so far and it involves a more complicated understanding of how to apply the chain rule. Needless to say in my simplification it should be noted that the inside function of $y = frac{N}{K}$ currently is in the same form of $(t - tau)$ as it is in $frac{dN}{dt}$ but by multiplying by $frac{1}{tau}$ the resultant inside will be of the form $(frac{t}{tau} - frac{tau}{tau}) = (x - 1)$. So my question is what needs to be done to further proceed along this problem? Any help would be much appreciated, thanks.










share|cite|improve this question


















  • 1




    $y = N/K$ is a little bit imprecise. More accurate is $y(x) = N(tau x)/K$. Does that help?
    – eyeballfrog
    Nov 14 at 6:47










  • @eyeballfrog So should I just distribute $tau$ in the inside function while letting $lambda = r$ to get the desired form or do I need to reassess what $frac{dy}{dN}$ should be using the more precise form of $y(x) = N(tau x)/K$?
    – Jmath99
    Nov 14 at 7:43













up vote
0
down vote

favorite









up vote
0
down vote

favorite











Hello I am trying to show that the equation



$frac{dN}{dt} = rN(1 - frac{N(t - tau)}{K})$



can be rewritten in a dimensionless form as



$frac{dy}{dx} = lambda y(1 - y(x - 1))$
using the transformations $y = frac{N}{K}$ and $x = frac{t}{tau}$.



So far my attempt at the problem is to assume $frac{dy}{dx} = frac{dy}{dN}*frac{dN}{dt}*frac{dt}{dx}$. Using the given information of $y = frac{N}{K}$ and $x = frac{t}{tau}$ it seems



$frac{dy}{dN} = frac{1}{K}$ and $frac{dx}{dt} = frac{1}{tau} Rightarrow frac{dt}{dx} = tau$



I then proceeded to substitute this information into $frac{dy}{dx} = frac{dy}{dN}*frac{dN}{dt}*frac{dt}{dx}$,



$frac{dy}{dx} = frac{1}{K}*(rN(1 - frac{N(t - tau)}{K}))*tau = rtau(frac{N}{K}(1 - frac{N}{K}(t - tau)) =$



$rtau y(1 - y(t - tau))$



At this point I am unsure if I should try to think of a factor to multiply the last step of my simplification so that I can assume $lambda$ is equal to some factor and then match it with what $frac{dy}{dx}$ is supposed to be or if I made a mistake in how I approached the problem so far and it involves a more complicated understanding of how to apply the chain rule. Needless to say in my simplification it should be noted that the inside function of $y = frac{N}{K}$ currently is in the same form of $(t - tau)$ as it is in $frac{dN}{dt}$ but by multiplying by $frac{1}{tau}$ the resultant inside will be of the form $(frac{t}{tau} - frac{tau}{tau}) = (x - 1)$. So my question is what needs to be done to further proceed along this problem? Any help would be much appreciated, thanks.










share|cite|improve this question













Hello I am trying to show that the equation



$frac{dN}{dt} = rN(1 - frac{N(t - tau)}{K})$



can be rewritten in a dimensionless form as



$frac{dy}{dx} = lambda y(1 - y(x - 1))$
using the transformations $y = frac{N}{K}$ and $x = frac{t}{tau}$.



So far my attempt at the problem is to assume $frac{dy}{dx} = frac{dy}{dN}*frac{dN}{dt}*frac{dt}{dx}$. Using the given information of $y = frac{N}{K}$ and $x = frac{t}{tau}$ it seems



$frac{dy}{dN} = frac{1}{K}$ and $frac{dx}{dt} = frac{1}{tau} Rightarrow frac{dt}{dx} = tau$



I then proceeded to substitute this information into $frac{dy}{dx} = frac{dy}{dN}*frac{dN}{dt}*frac{dt}{dx}$,



$frac{dy}{dx} = frac{1}{K}*(rN(1 - frac{N(t - tau)}{K}))*tau = rtau(frac{N}{K}(1 - frac{N}{K}(t - tau)) =$



$rtau y(1 - y(t - tau))$



At this point I am unsure if I should try to think of a factor to multiply the last step of my simplification so that I can assume $lambda$ is equal to some factor and then match it with what $frac{dy}{dx}$ is supposed to be or if I made a mistake in how I approached the problem so far and it involves a more complicated understanding of how to apply the chain rule. Needless to say in my simplification it should be noted that the inside function of $y = frac{N}{K}$ currently is in the same form of $(t - tau)$ as it is in $frac{dN}{dt}$ but by multiplying by $frac{1}{tau}$ the resultant inside will be of the form $(frac{t}{tau} - frac{tau}{tau}) = (x - 1)$. So my question is what needs to be done to further proceed along this problem? Any help would be much appreciated, thanks.







derivatives transformation chain-rule






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Nov 14 at 6:23









Jmath99

775




775








  • 1




    $y = N/K$ is a little bit imprecise. More accurate is $y(x) = N(tau x)/K$. Does that help?
    – eyeballfrog
    Nov 14 at 6:47










  • @eyeballfrog So should I just distribute $tau$ in the inside function while letting $lambda = r$ to get the desired form or do I need to reassess what $frac{dy}{dN}$ should be using the more precise form of $y(x) = N(tau x)/K$?
    – Jmath99
    Nov 14 at 7:43














  • 1




    $y = N/K$ is a little bit imprecise. More accurate is $y(x) = N(tau x)/K$. Does that help?
    – eyeballfrog
    Nov 14 at 6:47










  • @eyeballfrog So should I just distribute $tau$ in the inside function while letting $lambda = r$ to get the desired form or do I need to reassess what $frac{dy}{dN}$ should be using the more precise form of $y(x) = N(tau x)/K$?
    – Jmath99
    Nov 14 at 7:43








1




1




$y = N/K$ is a little bit imprecise. More accurate is $y(x) = N(tau x)/K$. Does that help?
– eyeballfrog
Nov 14 at 6:47




$y = N/K$ is a little bit imprecise. More accurate is $y(x) = N(tau x)/K$. Does that help?
– eyeballfrog
Nov 14 at 6:47












@eyeballfrog So should I just distribute $tau$ in the inside function while letting $lambda = r$ to get the desired form or do I need to reassess what $frac{dy}{dN}$ should be using the more precise form of $y(x) = N(tau x)/K$?
– Jmath99
Nov 14 at 7:43




@eyeballfrog So should I just distribute $tau$ in the inside function while letting $lambda = r$ to get the desired form or do I need to reassess what $frac{dy}{dN}$ should be using the more precise form of $y(x) = N(tau x)/K$?
– Jmath99
Nov 14 at 7:43















active

oldest

votes











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',
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
});


}
});














 

draft saved


draft discarded


















StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f2997871%2fapplying-chain-rule-to-dimensionless-transformation%23new-answer', 'question_page');
}
);

Post as a guest















Required, but never shown






























active

oldest

votes













active

oldest

votes









active

oldest

votes






active

oldest

votes
















 

draft saved


draft discarded



















































 


draft saved


draft discarded














StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f2997871%2fapplying-chain-rule-to-dimensionless-transformation%23new-answer', 'question_page');
}
);

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







Popular posts from this blog

Probability when a professor distributes a quiz and homework assignment to a class of n students.

Aardman Animations

Are they similar matrix