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#1 2007-04-01 14:53:53

Stanley_Marsh
Member
Registered: 2006-12-13
Posts: 345

Help

I have trouble with second derivative , I am not sure if I have skipped some

important rules , please help me step by step or point out my error.

here is what I did with (1)


Numbers are the essence of the Universe

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#2 2007-04-01 21:08:55

JaneFairfax
Member
Registered: 2007-02-23
Posts: 6,868

Re: Help

That seems to be the same answer as yours, isn’t it? smile

which is what you should expect for an origin-centred ellipse.

Last edited by JaneFairfax (2007-04-01 21:16:13)

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#3 2007-04-01 21:36:26

Stanley_Marsh
Member
Registered: 2006-12-13
Posts: 345

Re: Help

I checked my book , it said the answer is 


Like this one
, But the answer said it's
,HELPP!!!!PP!!P!

Last edited by Stanley_Marsh (2007-04-01 21:36:50)


Numbers are the essence of the Universe

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#4 2007-04-01 21:41:18

JaneFairfax
Member
Registered: 2007-02-23
Posts: 6,868

Re: Help

Argh, that’s a different curve!

is not an ellipse; it’s a hyperbola. The general equation for a hyperbola is

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#5 2007-04-01 21:56:41

JaneFairfax
Member
Registered: 2007-02-23
Posts: 6,868

Re: Help

I think we want an ellipse, not hyperbola, for this question, i.e.

And, actually, we could simplify what we had obtained earlier.

You were doing the right thing. You just needed to simplify the answer you had for the second derivative. smile

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#6 2007-04-02 02:21:10

Stanley_Marsh
Member
Registered: 2006-12-13
Posts: 345

Re: Help

OH!!!!!!! You can replace

  NEVER THOUGHT OF THAT!!!!

Last edited by Stanley_Marsh (2007-04-02 02:29:37)


Numbers are the essence of the Universe

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