Extensive replacement of trigonometric functions

*To*: mathgroup at smc.vnet.net*Subject*: [mg125007] Extensive replacement of trigonometric functions*From*: Mauro <pippo at hotmail.com>*Date*: Fri, 17 Feb 2012 06:26:41 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com

Hello to everybody. I have this problem: I would like to replace in a long expression all the occurrences of: Sin[\[Theta]_ + \[Pi]/6] and Sin[\[Theta]_ - \[Pi]/6] with respectively: -Cos[\[Theta] + (2 \[Pi])/3] and Cos[\[Theta] - (2 \[Pi])/3] (which actually are the same thing). Regretfully, the application of the rules: Sin[\[Theta]_ + \[Pi]/6] -> -Cos[\[Theta] + (2 \[Pi])/3] Sin[\[Theta]_ - \[Pi]/6] -> Cos[\[Theta] - (2 \[Pi])/3] results in a flop, since sine functions stubbornly appear again! Can you help me? Thank you in advance Mauro