Re: Question about trig simplify

*To*: mathgroup at smc.vnet.net*Subject*: [mg71131] Re: Question about trig simplify*From*: "dimitris" <dimmechan at yahoo.com>*Date*: Thu, 9 Nov 2006 03:37:39 -0500 (EST)*References*: <eisgno$ngg$1@smc.vnet.net>

You could say it is a feauture; not a bug (at least for me). Anyway Mathematica offers many opportunities for proper/desired simplifications/factorizations. It just needs to search a little more. TrigReduce /@ {-2*Sin[a]*Cos[a], 2*Sin[a]*Cos[a]} {-Sin[2*a], Sin[2*a]} Execute the following commands for more information FrontEndExecute[{HelpBrowserLookup["MainBook","3.3.7"]}] r = {{Cos[a], Sin[a]}, {-Sin[a], Cos[a]}}; r . r {{Cos[a]^2 - Sin[a]^2, 2*Cos[a]*Sin[a]}, {-2*Cos[a]*Sin[a], Cos[a]^2 - Sin[a]^2}} TrigReduce[%] {{Cos[2*a], Sin[2*a]}, {-Sin[2*a], Cos[2*a]}} TrigReduce[r . r . r] {{Cos[3*a], Sin[3*a]}, {-Sin[3*a], Cos[3*a]}} Regards Dimitris