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Topic: [ap-calculus] dx/dx?
Replies: 1   Last Post: Dec 20, 2011 8:24 AM

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Dosky, Douglas

Posts: 12
Registered: 2/23/09
RE: [ap-calculus] dx/dx?
Posted: Dec 20, 2011 8:24 AM
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I think this practice is helpful to understand the meaning of dy/dx and how it comes about. This practice also transitions well as we move the students into related rates. The students then get a better understanding of how dt comes into the picture and the algebra behind it.

Take care

Douglas A. Dosky
(c) 614-260-4699
email: ddosky@worthington.k12.oh.us
Thomas Worthington High School
AP Calculus BC and AB Teacher
________________________________________
From: Lin McMullin [lnmcmullin@aol.com]
Sent: Monday, December 19, 2011 10:36 PM
To: AP Calculus
Cc: AP Calculus
Subject: Re: [ap-calculus] dx/dx?

I've seen this done before. It serves to help kids and others to differentiate until you get to the variable, therefore they don't forget to differentiate y and get the dy/dx which kids and others sometimes do forget.

Lin

Lin McMullin
3520 Christopher Lane
Richardson, Texas 75082


On Dec 19, 2011, at 15:04, "Beth Gallis" <msgallis@comcast.net> wrote:

> When differentiating x^2+y^2=k implicitly, a colleague writes
>
> 2x* dx/dx + 2y* dy/dx =0. then 2x + 2y*dy/dx =0 since dx/dx =1.
>
> This seems like nonsense to me, since the derivative of x^2 with respect to x is just 2x - obviously x doesn't change with respect to x. Seems like a rote procedure so kids always put dsomething/dx.
>
> What do you all think?


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