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. >