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November 08, 2025, 05:19:01 am

Author Topic: Domain  (Read 1408 times)  Share 

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TrueTears

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Domain
« on: August 02, 2009, 07:09:33 pm »
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find the domain of

What's your method?
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kurrymuncher

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Re: Domain
« Reply #1 on: August 02, 2009, 07:30:42 pm »
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hmmm, just draw the original function without the modulus, then reflect everything above the x axis. then draw the gradient function, take the domain and exclude all the cusps and stuff.


yeah, so I guess it should be all real numbers except for -2

thats how I would do it, but Kamil probably has some pr0 method.


EDIT: I dont think its necessary to draw the gradient function. As long as you can see the cusp at -2, then you'll realise that the gradient is undefined at that point.
« Last Edit: August 02, 2009, 07:40:14 pm by kurrymuncher »

TrueTears

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Re: Domain
« Reply #2 on: August 02, 2009, 07:42:09 pm »
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hmmm, just draw the original function without the modulus, then reflect everything above the x axis. then draw the gradient function, take the domain and exclude all the cusps and stuff.


yeah, so I guess it should be all real numbers except for -2

thats how I would do it, but Kamil probably has some pr0 method.


EDIT: I dont think its necessary to draw the gradient function. As long as you can see the cusp at -2, then you'll realise that the gradient is undefined at that point.
Yeah exactly what I did kurrymuncher, thanks.

But yeah I was wondering if there is any rigorous algebraic non graphic method lol.
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Interested in asset pricing, econometrics, and social choice theory.

TrueTears

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Re: Domain
« Reply #3 on: August 02, 2009, 07:53:19 pm »
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In general... if the curve does not have any domain restrictions or asymptotes but does have cusps, then is the domain of the gradient function R \ {cusps} ?
PhD @ MIT (Economics).

Interested in asset pricing, econometrics, and social choice theory.

kurrymuncher

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Re: Domain
« Reply #4 on: August 02, 2009, 07:54:55 pm »
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In general... if the curve does not have any domain restrictions or asymptotes but does have cusps, then is the domain of the gradient function R \ {cusps} ?

Yep

TrueTears

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Re: Domain
« Reply #5 on: August 02, 2009, 07:55:45 pm »
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In general... if the curve does not have any domain restrictions or asymptotes but does have cusps, then is the domain of the gradient function R \ {cusps} ?

Yep
cool story bro (Y)
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/0

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Re: Domain
« Reply #6 on: August 02, 2009, 07:58:49 pm »
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For a function to be differentiable we require that

So is not differentiable.
« Last Edit: August 02, 2009, 08:02:11 pm by /0 »

TrueTears

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Re: Domain
« Reply #7 on: August 02, 2009, 08:03:19 pm »
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Thanks /0!
PhD @ MIT (Economics).

Interested in asset pricing, econometrics, and social choice theory.