Re: Trignometric rules
- To: mathgroup at smc.vnet.net
- Subject: [mg118199] Re: Trignometric rules
- From: Peter Pein <petsie at dordos.net>
- Date: Sat, 16 Apr 2011 07:34:22 -0400 (EDT)
- References: <io6d3h$drj$1@smc.vnet.net> <io8tn0$qam$1@smc.vnet.net>
Am 15.04.2011 09:56, schrieb Peter Pein: > 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 > Oops! Of course: tt /. Cos[pb:(s_. \[Phi]b /; Abs[s] == 1) + x_.] :> 2 Sin[s pb] Sin[x] sorry, Peter