ComplexExpand off by a factor of (-1)?

*To*: mathgroup at smc.vnet.net*Subject*: [mg129882] ComplexExpand off by a factor of (-1)?*From*: charles.ces at gmail.com*Date*: Fri, 22 Feb 2013 01:05:24 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net

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.

**Follow-Ups**:**Re: ComplexExpand off by a factor of (-1)?***From:*Raul Martinez <raulmart@mac.com>

**Re: ComplexExpand off by a factor of (-1)?***From:*Murray Eisenberg <murray@math.umass.edu>

**Re: ComplexExpand off by a factor of (-1)?***From:*Bob Hanlon <hanlonr357@gmail.com>