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Re: conversion of sin to cos

  • To: mathgroup at smc.vnet.net
  • Subject: [mg87088] Re: conversion of sin to cos
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Mon, 31 Mar 2008 02:06:04 -0500 (EST)
  • Organization: The Open University, Milton Keynes, UK
  • References: <fsnbe4$da2$1@smc.vnet.net>

glenn077 at gmail.com wrote:

> Here is my problem. I have a very long product of cosines with
> arguments of the form k*Pi, k being integers.
> I want to convert this expression to a sum of cosines. TrigReduce
> works fine, except that it converts cos to sin.
> So, I want all the sin (after the TrigReduce) to be converted to cos
> and the arguments be of the form p*Pi, p being rational of course.
> It has something to do with Hold or HoldAll, but I don't know the
> details. Or perhaps the TrigReduce can be overridden
> somehow.

Hi Glenn,

Please, could you post an actual (short) example of such a product as 
well as what you get having trigreduced it?

Meanwhile, Simplify/FullSimplify with the option ComplexityFunction 
might be what you are looking for.

Regards,
-- 
Jean-Marc


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