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Re: Difficulties with Re


On Monday 06 April 2009 03:05:13 am Aaron Fude wrote:
> Assuming[x > 0 && y > 0, Re[Exp[x + I y]] // Simplify]
> Assuming[x > 0 && y > 0, Re[Exp[(x + I y)^2]] // Simplify]

Hi, Aaron, 

   If you check the expansion of the second expression, you'll notice that it contains a part proportional to Exp[2ix*y]. This is generally complex for x>0 and y>0; if x*y is an integer multiple of pi, then the entire expression reduces to a real number; otherwise, the whole expression is imaginary. Unless you provide Mathematica (or anyone) more constraints on x and y, there is no way to tell you whether the whole thing has a real part, or whether the real part is zero. 



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