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MathGroup Archive 1997

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Re: trig expansion

  • To: mathgroup at
  • Subject: [mg8913] Re: [mg8854] trig expansion
  • From: Allan Hayes <hay at>
  • Date: Thu, 2 Oct 1997 22:57:07 -0400
  • Sender: owner-wri-mathgroup at

murray at (Murray Eisenberg)
[mg8854] trig expansion

> How can I cause Mathematica to expand
> 	Sin[2 Pi omega t + 2 Pi delta],
> where delta and omega are symbols, into the form
> Cos[2 Pi delta] Sin[2 Pi omega t]+Sin[2 Pi delta] Cos[2 Pi omega t]
> without using a replacment rule
>    Sin[a_ + b_] -> Sin[a]Cos[b] + Cos[a]Sin[b]

Here are four inelegant ways.

(Sin[2 delta \[Pi]+2 omega \[Pi] t]/. 2->k//TrigExpand)/.k->2

(Sin[x+y]//TrigExpand)/.{x->2 Pi omega t,y->2 Pi delta}

ReleaseHold[TrigExpand[Map[Hold,Sin[2 Pi omega t + 2 Pi delta],{2}]]]

   TrigExpand[Map[Identity,Sin[2 Pi omega t + 2 Pi delta],{2}]]

Allan Hayes
hay at
voice:+44 (0)116 2714198
fax: +44 (0)116 2718642
Leicester,  UK

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