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Re: real function argument

• To: mathgroup at smc.vnet.net
• Subject: [mg73418] Re: real function argument
• From: LBoogie <lwalker701 at earthlink.net>
• Date: Fri, 16 Feb 2007 00:54:22 -0500 (EST)
• References: <er1bq1$7ci$1@smc.vnet.net>

bar at ANTYSPAM.ap.krakow.pl wrote:
> Hi, 
> I have a problrm with defining real argument
> 
> In:   f[x_]:=Re[Cos[x]+I Sin[x]]
> 	f'[x]
> 
> Out:  -Cos[x] Im'[x]-Sin[x]Re'[x]
> 
> In: FullSimplify[f'[x],Element[x,Reals]] 
> gives the same out
> 
> Any suggestions ?


You can try

FullSimplify[f[x], Element[x,Reals]]

Then take the derivative of the result.