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 Post subject: 2nd order PDEPosted: Wed, 28 Mar 2012 16:14:51 UTC
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Hi there,

I have

I have to find and

The first part by chain rule:

I am not sure how to find from this though?

similarly

How do I go from this to the expression for ?

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 Post subject: Re: 2nd order PDEPosted: Wed, 28 Mar 2012 17:03:28 UTC
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Bazman wrote:
Hi there,

I have

I have to find and

The first part by chain rule:

I am not sure how to find from this though?

similarly

How do I go from this to the expression for ?

Be careful! Do you really mean in the last line?

Also, unless you do additional manipulations, you found is an explicit function of , not alone. So when you apply the chain rule you need to use

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 Post subject: Re: 2nd order PDEPosted: Wed, 28 Mar 2012 17:14:57 UTC
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thanks OM and yes should have been

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 Post subject: Re: 2nd order PDEPosted: Wed, 28 Mar 2012 17:26:42 UTC
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Location: Austin, TX
Bazman wrote:
thanks OM and yes should have been

??

I'm confused, why not just make the substitutions?

Then and use one variable calculus?

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 Post subject: Re: 2nd order PDEPosted: Wed, 28 Mar 2012 18:04:30 UTC
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umm its a good point, but the unit we are working on is PDE's and it explicitly reuqests you use PSE's to solve it.

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 Post subject: Re: 2nd order PDEPosted: Wed, 28 Mar 2012 18:33:41 UTC
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Bazman wrote:
umm its a good point, but the unit we are working on is PDE's and it explicitly reuqests you use PSE's to solve it.

I suppose. I guess I always think of ODEs as a subset of PDEs. In any case, this is a good way to check your work.

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 Post subject: Re: 2nd order PDEPosted: Wed, 28 Mar 2012 18:36:58 UTC
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Thanks Shadow, your method is clearly better.

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