Re: Transforming a polynomial into a trigonometric format tia sal2

*To*: mathgroup at smc.vnet.net*Subject*: [mg88299] Re: Transforming a polynomial into a trigonometric format tia sal2*From*: ratullochjk2 at gmail.com*Date*: Thu, 1 May 2008 03:19:51 -0400 (EDT)*References*: <fv42j9$5ui$1@smc.vnet.net>

I'm sorry if I didn't explain myself better I hope this clarifies it better when I test for x =3 x= 7 for equation: 21 - 10 x + x^2 I get zero for both answers I used another math program using the ChebyshevT command and I got this 1/2 Cos[2 ArcCos[x]] + 43/2 - 10 x I tested with x=3 and x=7 and I also got zero for both but when I do a TrigReduce In[148] := 21 - 10 x + x^2 /. x -> Cos[y] // TrigReduce I get Out[149]:= 1/2 (43 - 20 Cos[x] + Cos[2 x]) x=3 gives me 31.88 x=7 gives me 14.0293 I would like to use the ChebyshevT in mathematica 6 because I prefer that software but I'm not sure how to get the 1/2 Cos[2 ArcCos[x]] + 43/2 - 10 x answer in mathematica 6 Am I doing something wrong with the TrigReduce function or leaving a part out why are the answers not even close? tia sal2 On Apr 27, 10:41 pm, ratulloch... at gmail.com wrote: > Transforming a polynomial into a trigonometric format tiasal2 > > Greetings All > > I'm using mathematica 6 and I have a polynomial and would like to > convert it into > a Trigonometric format. Is this possible? > > Example: > I have a polynomial > 0.00154991- 4.01371 x + 1.81197 x^2 + 8.00183 x^3 - 9.3462 x^4 > > How can I transform this into a trigonometric format > Example: > 0.00596679 Cos[6.98132 x] + 0.00358397 Cos[7.21403 x] + > 2.25013 Sin[0.232711 x] - 4.51511 Sin[0.465421 x] > > Note: these aren't correct answers I just wanted to include and > example > > tiasa

**Follow-Ups**:**Re: Re: Transforming a polynomial into a trigonometric format tia sal2***From:*"Szabolcs HorvÃt" <szhorvat@gmail.com>

**Re: Re: Transforming a polynomial into a trigonometric format tia sal2***From:*Andrzej Kozlowski <akoz@mimuw.edu.pl>