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Re: ComplexExpand off by a factor of (-1)?

• To: mathgroup at smc.vnet.net
• Subject: [mg129890] Re: ComplexExpand off by a factor of (-1)?
• From: Murray Eisenberg <murray at math.umass.edu>
• Date: Sat, 23 Feb 2013 07:01:46 -0500 (EST)
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• References: <20130222060524.703B768D0@smc.vnet.net>

Hint: in your expression, replace 2*I by 2*k and you'll see why Mathematica gave you the correct value, i.e., exactly what you asked for!
On Feb 22, 2013, at 1:05 AM, charles.ces at gmail.com wrote:

> Would someone be able to help me understand why when I enter the expression:
>
> ComplexExpand[(E^(I*y) - E^(-I*y))/2*I] I get a result of -Sin[y] instead of Sin[y]?
>
> Thanks.
>
> Charles S.

---
Murray Eisenberg                                    murray at math.umass.edu
Mathematics & Statistics Dept.      
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University of Massachusetts                               413 545-2838 (W)
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• References:
  • ComplexExpand off by a factor of (-1)?
    • From: charles.ces@gmail.com