Re: Mathmatica Problem...
- To: mathgroup at smc.vnet.net
- Subject: [mg14344] Re: Mathmatica Problem...
- From: "Allan Hayes" <hay at haystack.demon.co.uk>
- Date: Thu, 15 Oct 1998 00:28:47 -0400
- References: <6vuqt7$8ju@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Mr D.J. Winstanley wrote in message <6vuqt7$8ju at smc.vnet.net>...
>
>Dear mathgroup,
>
>We have just upgraded to release 3 of mathematica and we have found a
>problem with the Expand function as described in the mathematica
>manual. Here is the mathematica 3.0 output...
>
>
>In[3]:= Expand[Cos[x]^3 Sin[x]^2,Trig->True]
>
>gives
>
> 3 2
>Out[3]= Cos[x] Sin[x]
>
>
>this is not the answer given in the manual, which is...
>
> Cos[x] - Cos[3 x] - Cos[5 x]
> ------ -------- --------
> 8 16 16
>
>
>We were led to believe that the new version was compatible with the
>previous version.
>
>Is there a switch to obtain compatibility???
>
>Any comments on this would be appreciated. Also who should I send this
>to at Wolfram?
>
>thanks for your help
>
David,
I don't have Mathematica 2.2 anymore - can you give the reference to the
manual information that you quote please?
I also get
cs =Cos[x]^3 Sin[x]^2;
Expand[Cos[x]^3 Sin[x]^2,Trig->True]
3 2
Cos[x] Sin[x]
But that is what I would expect.
The following two evaluations give the result that you quote from the
manual (up to multiplying out).
TrigReduce[cs]
1
-- (2 Cos[x] - Cos[3 x] - Cos[5 x])
16
Apart[cs,Trig->True]
Cos[x] 1 1
------ - -- Cos[3 x] - -- Cos[5 x]
8 16 16
----------------------
Allan Hayes
Mathematica Training and Consulting
www.haystack.demon.co.uk
hay at haystack.demon.co.uk
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565