Solution to nonlinear ODE using Contraction Mapping Theorem.
I need to use the contraction mapping theorem to prove that a solution exists to the IVP $y' = sin(x)sin(y),; y(1)=2$, on the interval $;[1,1+h],; h>0$.
My attempt at the solution. Let $E = C^1([1,1+h])$ ($h$ remains to be chosen). Let $;d;$ be the usual function space metric. Then $(E,d)$ forms a complete metric space.
Define the map $T:Eto E$ by the rule $(Ty)(x)=2+intlimits_1^x sin(s)sin(y(s))ds$.
Let $y_1,y_2in E$.
WTS: $d(Ty_1,Ty_2)leq rd(y_1,y_2)$, with $0<r<1$.
By plugging in the expression for $;d(Ty_1,Ty_2),;$ I was able to perform a few algebraic manipulations to get to
$$d(Ty_1,Ty_2) leq Mintlimits_1^{1+h}|sin(y_1(s)-sin(y_2(s))|,$$
where $M$ came from the fact that $sin(x)$ is bounded. From here I got the expression:
$$d(Ty_1,Ty_2)leq Mhleft(sup_{xepsilon[1,1+h]}|sin(y_1(s)-sin(y_2(s))|right).$$
Here is where I got stuck. Usually, in the linear ODE and systems case, the absolute value is just $d(y_1,y_2)$, and then I can choose $h<frac{1}{M}$ and be done, but here I have the functions composed inside of the sine? How do I proceed from here?
real-analysis
add a comment |
I need to use the contraction mapping theorem to prove that a solution exists to the IVP $y' = sin(x)sin(y),; y(1)=2$, on the interval $;[1,1+h],; h>0$.
My attempt at the solution. Let $E = C^1([1,1+h])$ ($h$ remains to be chosen). Let $;d;$ be the usual function space metric. Then $(E,d)$ forms a complete metric space.
Define the map $T:Eto E$ by the rule $(Ty)(x)=2+intlimits_1^x sin(s)sin(y(s))ds$.
Let $y_1,y_2in E$.
WTS: $d(Ty_1,Ty_2)leq rd(y_1,y_2)$, with $0<r<1$.
By plugging in the expression for $;d(Ty_1,Ty_2),;$ I was able to perform a few algebraic manipulations to get to
$$d(Ty_1,Ty_2) leq Mintlimits_1^{1+h}|sin(y_1(s)-sin(y_2(s))|,$$
where $M$ came from the fact that $sin(x)$ is bounded. From here I got the expression:
$$d(Ty_1,Ty_2)leq Mhleft(sup_{xepsilon[1,1+h]}|sin(y_1(s)-sin(y_2(s))|right).$$
Here is where I got stuck. Usually, in the linear ODE and systems case, the absolute value is just $d(y_1,y_2)$, and then I can choose $h<frac{1}{M}$ and be done, but here I have the functions composed inside of the sine? How do I proceed from here?
real-analysis
Please consider a better formatting for your question. Actually it is kinda hard to read.
– nicomezi
Nov 29 at 10:10
1
I rewrote the post to be more readable
– Anonymous Snake
Nov 29 at 10:23
Thank you for your edit.
– nicomezi
Nov 29 at 10:24
add a comment |
I need to use the contraction mapping theorem to prove that a solution exists to the IVP $y' = sin(x)sin(y),; y(1)=2$, on the interval $;[1,1+h],; h>0$.
My attempt at the solution. Let $E = C^1([1,1+h])$ ($h$ remains to be chosen). Let $;d;$ be the usual function space metric. Then $(E,d)$ forms a complete metric space.
Define the map $T:Eto E$ by the rule $(Ty)(x)=2+intlimits_1^x sin(s)sin(y(s))ds$.
Let $y_1,y_2in E$.
WTS: $d(Ty_1,Ty_2)leq rd(y_1,y_2)$, with $0<r<1$.
By plugging in the expression for $;d(Ty_1,Ty_2),;$ I was able to perform a few algebraic manipulations to get to
$$d(Ty_1,Ty_2) leq Mintlimits_1^{1+h}|sin(y_1(s)-sin(y_2(s))|,$$
where $M$ came from the fact that $sin(x)$ is bounded. From here I got the expression:
$$d(Ty_1,Ty_2)leq Mhleft(sup_{xepsilon[1,1+h]}|sin(y_1(s)-sin(y_2(s))|right).$$
Here is where I got stuck. Usually, in the linear ODE and systems case, the absolute value is just $d(y_1,y_2)$, and then I can choose $h<frac{1}{M}$ and be done, but here I have the functions composed inside of the sine? How do I proceed from here?
real-analysis
I need to use the contraction mapping theorem to prove that a solution exists to the IVP $y' = sin(x)sin(y),; y(1)=2$, on the interval $;[1,1+h],; h>0$.
My attempt at the solution. Let $E = C^1([1,1+h])$ ($h$ remains to be chosen). Let $;d;$ be the usual function space metric. Then $(E,d)$ forms a complete metric space.
Define the map $T:Eto E$ by the rule $(Ty)(x)=2+intlimits_1^x sin(s)sin(y(s))ds$.
Let $y_1,y_2in E$.
WTS: $d(Ty_1,Ty_2)leq rd(y_1,y_2)$, with $0<r<1$.
By plugging in the expression for $;d(Ty_1,Ty_2),;$ I was able to perform a few algebraic manipulations to get to
$$d(Ty_1,Ty_2) leq Mintlimits_1^{1+h}|sin(y_1(s)-sin(y_2(s))|,$$
where $M$ came from the fact that $sin(x)$ is bounded. From here I got the expression:
$$d(Ty_1,Ty_2)leq Mhleft(sup_{xepsilon[1,1+h]}|sin(y_1(s)-sin(y_2(s))|right).$$
Here is where I got stuck. Usually, in the linear ODE and systems case, the absolute value is just $d(y_1,y_2)$, and then I can choose $h<frac{1}{M}$ and be done, but here I have the functions composed inside of the sine? How do I proceed from here?
real-analysis
real-analysis
edited Nov 29 at 17:29
user376343
2,7782822
2,7782822
asked Nov 29 at 10:05
Anonymous Snake
162
162
Please consider a better formatting for your question. Actually it is kinda hard to read.
– nicomezi
Nov 29 at 10:10
1
I rewrote the post to be more readable
– Anonymous Snake
Nov 29 at 10:23
Thank you for your edit.
– nicomezi
Nov 29 at 10:24
add a comment |
Please consider a better formatting for your question. Actually it is kinda hard to read.
– nicomezi
Nov 29 at 10:10
1
I rewrote the post to be more readable
– Anonymous Snake
Nov 29 at 10:23
Thank you for your edit.
– nicomezi
Nov 29 at 10:24
Please consider a better formatting for your question. Actually it is kinda hard to read.
– nicomezi
Nov 29 at 10:10
Please consider a better formatting for your question. Actually it is kinda hard to read.
– nicomezi
Nov 29 at 10:10
1
1
I rewrote the post to be more readable
– Anonymous Snake
Nov 29 at 10:23
I rewrote the post to be more readable
– Anonymous Snake
Nov 29 at 10:23
Thank you for your edit.
– nicomezi
Nov 29 at 10:24
Thank you for your edit.
– nicomezi
Nov 29 at 10:24
add a comment |
1 Answer
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For $a,b in mathbb R$ we have, by the mean value theorem:
$| sin(b)-sin(a)| le |b-a|$.
Thus $| sin(y_1(s))-sin(y_2(s))| le |y_1(s)-y_2(s)| le d(y_1,y_2).$
Thank you so much!
– Anonymous Snake
Nov 29 at 10:23
add a comment |
Your Answer
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1 Answer
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1 Answer
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For $a,b in mathbb R$ we have, by the mean value theorem:
$| sin(b)-sin(a)| le |b-a|$.
Thus $| sin(y_1(s))-sin(y_2(s))| le |y_1(s)-y_2(s)| le d(y_1,y_2).$
Thank you so much!
– Anonymous Snake
Nov 29 at 10:23
add a comment |
For $a,b in mathbb R$ we have, by the mean value theorem:
$| sin(b)-sin(a)| le |b-a|$.
Thus $| sin(y_1(s))-sin(y_2(s))| le |y_1(s)-y_2(s)| le d(y_1,y_2).$
Thank you so much!
– Anonymous Snake
Nov 29 at 10:23
add a comment |
For $a,b in mathbb R$ we have, by the mean value theorem:
$| sin(b)-sin(a)| le |b-a|$.
Thus $| sin(y_1(s))-sin(y_2(s))| le |y_1(s)-y_2(s)| le d(y_1,y_2).$
For $a,b in mathbb R$ we have, by the mean value theorem:
$| sin(b)-sin(a)| le |b-a|$.
Thus $| sin(y_1(s))-sin(y_2(s))| le |y_1(s)-y_2(s)| le d(y_1,y_2).$
answered Nov 29 at 10:13
Fred
44.2k1645
44.2k1645
Thank you so much!
– Anonymous Snake
Nov 29 at 10:23
add a comment |
Thank you so much!
– Anonymous Snake
Nov 29 at 10:23
Thank you so much!
– Anonymous Snake
Nov 29 at 10:23
Thank you so much!
– Anonymous Snake
Nov 29 at 10:23
add a comment |
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Please consider a better formatting for your question. Actually it is kinda hard to read.
– nicomezi
Nov 29 at 10:10
1
I rewrote the post to be more readable
– Anonymous Snake
Nov 29 at 10:23
Thank you for your edit.
– nicomezi
Nov 29 at 10:24