Re: Exact value of Cos[Pi/17]

*To*: mathgroup at smc.vnet.net*Subject*: [mg14871] Re: Exact value of Cos[Pi/17]*From*: "Allan Hayes" <hay at haystack.demon.co.uk>*Date*: Mon, 23 Nov 1998 10:11:51 -0500*Sender*: owner-wri-mathgroup at wolfram.com

I have received several mails that this is expansion is not working with Mathematica 3.0x. Sorry, I find that I was using a beta test copy of the next version. Allan --------------------- Allan Hayes Mathematica Training and Consulting www.haystack.demon.co.uk hay at haystack.demon.co.uk Voice: +44 (0)116 271 4198 Fax: +44 (0)870 164 0565 Allan Hayes wrote in message ... > >Christopher Gorski wrote in message <72tt9f$isg at smc.vnet.net>... >>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. >> >>-- >>Christopher Gorski >>cgorski at adelphia.net >>http://www.contrib.andrew.cmu.edu/~cgorski >> >> >> > >Christopher (using InputForm for Output cells) > >Cos[Pi/17] > >Cos[Pi/17] > >FunctionExpand[%] > >1/4*Sqrt[1/2*(15 + Sqrt[17] + Sqrt[2*(17 - Sqrt[17])] + > Sqrt[2*(34 + 6*Sqrt[17] - Sqrt[2*(17 - Sqrt[17])] + > Sqrt[34*(17 - Sqrt[17])] - > 8*Sqrt[2*(17 + Sqrt[17])])])] > >?FunctionExpand > >"FunctionExpand[expr] tries to expand out special and certain other >functions \ >in expr, when possible reducing compound arguments to simpler ones. \ >FunctionExpand[expr, assum] expands using assumptions." > >Allan > > > >