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Thread Subject:
how do i unwrap 'arcsin' function?

Subject: how do i unwrap 'arcsin' function?

From: flying

Date: 1 Jun, 2012 16:46:25

Message: 1 of 5

Hi all!
    i've encountered a problem.As we know the range of 'arcsin' in matlab is -pi/2~pi/2.
if we do asin(sin(t)),t= 0:10;we get an wrap answer,but now i want to retrieve the 't',how can i get the original 't'? Thank you!

and we may also encouter such a problem about elliptic integral.For example .elliptic integral of third kind,and it's also period function.My question is how i can get a monotone function.

Subject: how do i unwrap 'arcsin' function?

From: Matt J

Date: 1 Jun, 2012 18:38:22

Message: 2 of 5

"flying" wrote in message <jqarl1$dkk$1@newscl01ah.mathworks.com>...
> Hi all!
> i've encountered a problem.As we know the range of 'arcsin' in matlab is -pi/2~pi/2.
> if we do asin(sin(t)),t= 0:10;we get an wrap answer,but now i want to retrieve the 't',how can i get the original 't'? Thank you!
========

You cannot, due to sin(t) not being 1-1.

Subject: how do i unwrap 'arcsin' function?

From: flying

Date: 2 Jun, 2012 02:56:26

Message: 3 of 5

"Matt J" wrote in message <jqb26t$dm0$1@newscl01ah.mathworks.com>...
> "flying" wrote in message <jqarl1$dkk$1@newscl01ah.mathworks.com>...
> > Hi all!
> > i've encountered a problem.As we know the range of 'arcsin' in matlab is -pi/2~pi/2.
> > if we do asin(sin(t)),t= 0:10;we get an wrap answer,but now i want to retrieve the 't',how can i get the original 't'? Thank you!
> ========
>
> You cannot, due to sin(t) not being 1-1.


the range of 't' is 0~10 and my target is retrieving 't'

Subject: how do i unwrap 'arcsin' function?

From: TideMan

Date: 2 Jun, 2012 03:02:40

Message: 4 of 5

On Saturday, June 2, 2012 4:46:25 AM UTC+12, flying wrote:
> Hi all!
> i've encountered a problem.As we know the range of 'arcsin' in matlab is -pi/2~pi/2.
> if we do asin(sin(t)),t= 0:10;we get an wrap answer,but now i want to retrieve the 't',how can i get the original 't'? Thank you!
>
> and we may also encouter such a problem about elliptic integral.For example .elliptic integral of third kind,and it's also period function.My question is how i can get a monotone function.

help unwrap

Subject: how do i unwrap 'arcsin' function?

From: Matt J

Date: 2 Jun, 2012 17:26:32

Message: 5 of 5

"flying" wrote in message <jqbvcq$d93$1@newscl01ah.mathworks.com>...
>
> > You cannot, due to sin(t) not being 1-1.
>
>
> the range of 't' is 0~10 and my target is retrieving 't'
==============

It is a target you will not be able to achieve.
sin(t) is not 1-1 on the interval 0<=t<=10

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