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MathGroup Archive 2005

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Re: TrigExpand - Odd behavior

  • To: mathgroup at smc.vnet.net
  • Subject: [mg55427] Re: TrigExpand - Odd behavior
  • From: dh <dh at metrohm.ch>
  • Date: Wed, 23 Mar 2005 05:34:38 -0500 (EST)
  • References: <d1on7b$nda$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Bob Stagat wrote:
> Try executing the following three lines and explain the last result...
> 
> Cos[45 Degree]
> 
> Cos[x+45 Degree]
> 
> Cos[x+45 Degree]//TrigExpand
> 
> Thanks...
> ~ BS ~
> 

Hello Bob,
"Degree" has an accurate value of 180/Pi. Mathematica will not replace 
accurate expressions by expressions having machine precision. Therefore:
Sin[1 Degree]
will not evaluate, however this will:
Sin[45 Degree]
because there is a closed form accurate answer. Also the following will 
evaluate:
Sin[1. Degree]
because 1. Degree has machine precission.

Your output looks rather strange because Degree is printed by a small o. 
This may look bizare, but it still means 180/Pi.

Daniel


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