From: dhart@appollonius.ucs.indiana.edu (Dave Hart)
Newsgroups: sci.math.symbolic
Subject: Re: Cos[a+b] --> Cos[a]*Cos[b]...etc. in Mathematica?
Date: 27 Nov 1995 15:17:08 GMT

In article <1995Nov26.162447.3425@news.wrc.xerox.com>, peter@eml4 (Peter A. Torpey 716-422-0470) writes:
|> 
|> What is the switch or control in Mathematica to expand
|> trig functions of sums of angles into trig
|> functions of the angles and vice versa?

   Simplify[ Sin[a + b] ] 
returns 
   Sin[a] Cos[b] + Cos[a] Sin[b] 

After
   <<Algebra`Trigonometry`

   TrigReduce[Sin[a + b]]
returns  
   Cos[b] Sin[a] + Cos[a] Sin[b]


This is in the IU database [http://sckb.ucssc.indiana.edu/kb/] -
search on "mathematica" [or "mathematica trigonometry" to reduce 
the number of hits]. 

=================================================
David Hart    <http://www.indiana.edu/~statmath/>
Center for Statistical and Mathematical Computing
Indiana University          Bloomington, IN 47405