Re: Exact value of Cos[Pi/17]
- To: mathgroup at smc.vnet.net
- Subject: [mg21085] Re: Exact value of Cos[Pi/17]
- From: "Stephen P Luttrell" <luttrell at signal.dra.hmg.gb>
- Date: Sun, 12 Dec 1999 23:51:53 -0500 (EST)
- Organization: Defence Evaluation and Research Agency
- References: <72tt9f$isg@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
>In The Mathematica Book, there is an example on page 936 of Mathematica >returning the exact answer to Cos[Pi/17]. When I try it out on my NT >machine, however, (mathematica v.3), it simply returns Cos[Pi/17]. >I've searched throughout the book, and I can't figure out how to get my >system to return a answer as in the example given. It will return >simple things, Cos[Pi], for example, returns -1, but more complex >arguments won't work. In Mathematica 3 the following input: TrigExpand[Cos[Pi/17]] gives the following output: (1*(-1)^(1/17))/2 - (1*(-1)^(16/17))/2 Stephen P Luttrell Signal Processing and Imagery Department DERA Malvern, St.Andrew's Road Malvern, United Kingdom, WR14 3PS +44 (0)1684 894046 (tel) +44 (0)1684 894384 (fax) luttrell at signal.dera.gov.uk (email)