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MathGroup Archive 2005

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Re: TrigExpand - Odd behavior

  • To: mathgroup at
  • Subject: [mg55440] Re: TrigExpand - Odd behavior
  • From: "David Park" <djmp at>
  • Date: Wed, 23 Mar 2005 05:34:51 -0500 (EST)
  • Sender: owner-wri-mathgroup at


That does seem like a bug - or at least a feature. But the following

Cos[x + 45 Degree] // N // TrigExpand // Chop
0.707107 Cos[x] - 0.707107 Sin[x]

Cos[x + Pi/4] // TrigExpand
Cos[x]/Sqrt[2] - Sin[x]/Sqrt[2]

David Park
djmp at

From: Bob Stagat [mailto:stagat at]
To: mathgroup at

Try executing the following three lines and explain the last result...

Cos[45 Degree]

Cos[x+45 Degree]

Cos[x+45 Degree]//TrigExpand

~ BS ~

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