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Re: Extract coefficients of a trig polynomial

• To: mathgroup at smc.vnet.net
• Subject: [mg126146] Re: Extract coefficients of a trig polynomial
• From: Yi Wang <tririverwangyi at gmail.com>
• Date: Fri, 20 Apr 2012 07:49:48 -0400 (EDT)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• References: <jmoge7$46g$1@smc.vnet.net>

Hi, Sam,

The following may help. But it may be not as general as you want.

Coefficient[expr, #] & /@ {Cos[2 \[Theta]], Cos[4 \[Theta]], 
  Cos[6 \[Theta]]}