       Re: A question of simplification

• To: mathgroup at smc.vnet.net
• Subject: [mg21023] Re: [mg20953] A question of simplification
• From: BobHanlon at aol.com
• Date: Thu, 2 Dec 1999 21:41:34 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

```If you mean to multiply c and f[x] rather than take their dot product then it
works as you intend

D[c*f[x], x]

c*Derivative[f][x]

Otherwise, tell it that a dot product with zero is zero

D[c . f[x], x] /. 0 . x_ :> 0

c . Derivative[f][x]

Bob Hanlon

In a message dated 12/1/1999 3:25:49 AM, eexiong at ee.ust.hk writes:

>In Mathematica, when using partial differentiation, we get
>D[c.f[x]]=0.f[x]+c.f'[x], not c.f'[x]. So, when the equation is long,
>the result will be very tedious.
>How can I simply the result to c.f'[x]? I have tested Simplify and
>FullSimplify. It does not work.
>

```

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