Re: ChebyshevT command syntax and polynomial question using mathematica

*To*: mathgroup at smc.vnet.net*Subject*: [mg88287] Re: ChebyshevT command syntax and polynomial question using mathematica*From*: Szabolcs Horvát <szhorvat at gmail.com>*Date*: Wed, 30 Apr 2008 07:03:11 -0400 (EDT)*Organization*: University of Bergen*References*: <fv9af1$ms0$1@smc.vnet.net>

ratullochjk2 at gmail.com wrote: > Greetings All > > I execute the command and get the following output: > > In[83] := FunctionExpand[1/2 Cos[2 ArcCos[x]] + 43/2 - 10 x] // Expand > Out[83]:= 21 - 10 x + x^2 > > What would be the proper format to execute the polynomial using > ChebyshevT to do it in reverse order? > > Example: > I would input > In[83] := FunctionExpand[ChebyshevT[n, x]] > and it gives me > Out[83]:= Cos[n ArcCos[x]] > > How can I do a > In[83] := FunctionExpand[ChebyshevT[n, x]] > and it would give me > Out[83]:= 1/2 Cos[2 ArcCos[x]] + 43/2 - 10 x Use TrigReduce: 21 - 10 x + x^2 /. x -> Cos[y] // TrigReduce