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Re: Wrong partial derivatives calculated

  • To: mathgroup at smc.vnet.net
  • Subject: [mg41183] Re: Wrong partial derivatives calculated
  • From: Bill Rowe <listuser at earthlink.net>
  • Date: Tue, 6 May 2003 06:05:31 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

On 5/5/03 at 2:40 AM, david at hushmail.com (David) wrote:

>When I calculate (D[x^2 + xy + y^2, x) mathematica gives me 2y and
>when I calculate D[x^2 + xy + y^2, y) I get 2x.  These are wrong
>answers -- have I got the syntax right?  I'm trying to find partial
>derivatives of x^2 + xy + y^2 with respect to x and y.

Exactly what are you inputing? Niether expression above is complete Mathematica syntax.

When I type

D[x^2 + xy + y^2, x]

I get

2 x since xy is a symbol named independent of x, not the product of x and y

But when I type

D[x^2 + x y + y^2, x]

I get

2 x + y


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