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Re: conversion of sin to cos

• To: mathgroup at smc.vnet.net
• Subject: [mg87104] Re: conversion of sin to cos
• From: dh <dh at metrohm.ch>
• Date: Tue, 1 Apr 2008 03:19:56 -0500 (EST)
• References: <fsnbe4$da2$1@smc.vnet.net>

Hi,

you may simply replace all Sin[x] -> Cos[x-Pi/2]

hope this helps, Daniel





glenn077 at gmail.com wrote:

> Hello all,

> 

> 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.

> Can someone help?

> Thank's for your time.

>