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Groups > comp.soft-sys.math.mathematica > #1698

Re: Trignometric rules

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Am 14.04.2011 11:00, schrieb Chelly:
> I have an expression as hsown below
>
> tt = -4 k1^2 v^2 \[Epsilon]1^2 \[Epsilon]c^2 Cos[2 d1 + d2 + d3] -
>     2 k1 k2 u^2 \[Epsilon]1 Cos[d1 + d2 - \[Phi]b - \[Phi]r] +
>     2 k1^2 v^2 \[Epsilon]1^2 \[Epsilon]c^2 Cos[
>       2 d1 + d2 + d3 - \[Phi]b - \[Phi]r] +
>     2 k1^3 k2 v^2 \[Epsilon]1^3 \[Epsilon]c^2 Cos[
>       d1 + d3 + \[Phi]b + \[Phi]r] +
>     2 k1^2 u^2 \[Epsilon]1^2 Cos[2 d1 + d2 + d3 + \[Phi]b + \[Phi]r] -
>     2 k1^2 v^2 \[Epsilon]1^2 \[Epsilon]c^2 Cos[
>       2 d1 + d2 + d3 + \[Phi]b + \[Phi]r];
>
> I'd like to replace any term containing Cos[+/- phib + x_]  with 2 Sin [+/-phib] Sin[x]. How do I go about doing it.
>
> Thanks
> Chelly
>

Hi Chelly,

use pattern matching:

tt /. Cos[pb:(s_. \[Phi]b /; Abs[s] == 1) + x_.] :> 2 Sin[pb] Sin[x]

Peter

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Trignometric rules Chelly <chelly85086@gmail.com> - 2011-04-14 09:00 +0000
  Re: Trignometric rules Peter Pein <petsie@dordos.net> - 2011-04-15 07:56 +0000
    Re: Trignometric rules Peter Pein <petsie@dordos.net> - 2011-04-16 11:34 +0000

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