Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2001
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2001

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Rewriting of Trigonometric Functions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg26843] Re: Rewriting of Trigonometric Functions
  • From: "Paul Lutus" <nospam at nosite.com>
  • Date: Thu, 25 Jan 2001 01:13:21 -0500 (EST)
  • References: <94m8st$3mn@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

"Thomas Engelhardt" <thomas-a.engelhardt at t-online.de> wrote in message
news:94m8st$3mn at smc.vnet.net...
> Dear Mathgroup members,
>
> I have just started to use Mathematica and directly ran into a problem:
>
> I have rather lengthy expressions resulting from putting a sum of two
> sinusodial swings to the power of three (Two-tone Intermodulation).
> In order for me to recognise the contained frequencies I want Mathematica
to
> rewrite the contained Trigonometric functions in certain ways, namely
like:
>
> [sin(a)]^2  should be transformed into 1/2*(1+cos2x)
> and for higher powers accordingly.
>
> Furthermore:
> sin(a)*sin(b) should be changed to 1/2*[cos(a-b) - cos(a+b)]
>
> I have tried all kinds of "Expand" and "Trig..." operations but
Mathematica
> always keeps the powers on the trigonometric functions and doesn't change
> the multiplications either.
>
> Does anybody have an idea how I can get Mathematica to transform the
> expressions in the desired way?

Why not write your own functions and use them instead of the default
functions? This is by far the simplest way to get a non-standard treatment
of the described functions.

--
Paul Lutus
www.arachnoid.com





  • Prev by Date: Re: exporting animations
  • Next by Date: Re: reference
  • Previous by thread: Re: Rewriting of Trigonometric Functions
  • Next by thread: Re: Rewriting of Trigonometric Functions