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