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

• To: mathgroup at smc.vnet.net
• Subject: [mg129894] Re: ComplexExpand off by a factor of (-1)?
• From: Raul Martinez <raulmart at mac.com>
• Date: Sat, 23 Feb 2013 07:03:06 -0500 (EST)
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• Delivered-to: l-mathgroup@wolfram.com
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• References: <20130222060524.703B768D0@smc.vnet.net>

The reason is that the denominator should be (2*I) instead of 2*I. As it stands, the expression (E^(I*y) - E^(-I*y))/2*I is interpreted as I*(E^(I*y) - E^(-I*y))/2.

Raul

On Feb 21, 2013, at 10:05 PM, 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.
>

• References:
  • ComplexExpand off by a factor of (-1)?
    • From: charles.ces@gmail.com