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 Author Comment/Response Kevin 10/12/07 4:28pm I am using Mathematica 6.0.0 and have run into what appears to be an inconsistency with the ArcCos function. ArcCos[1] returns 0. But ArcCos[exp], where exp evaluates to 1, returns a complex number not equal to 0. Below I copied a Mathematica notebook that illustrates my question. I have also attached the notebook to this message. In[1]:= (* Compute an expression *) a = 17.0677; b = 1; c = 18.0677; exp = (-a^2 + b^2 + c^2)/(2 b c) Out[4]= 1. In[5]:= (* Verify that the expression equals 1 *) exp == 1 Out[5]= True In[6]:= (* ArcCos of 1 equals 0, as expected *) ArcCos[1] Out[6]= 0 In[7]:= (* But ArcCos of our expression doesn't equal 1 *) ArcCos[exp] Out[7]= 0.+ 2.10734*10^-8 \[ImaginaryI] Attachment: ArcCos.nb, URL: ,

 Subject (listing for 'Inconsistent ArcCos Behavior') Author Date Posted Inconsistent ArcCos Behavior Kevin 10/12/07 4:28pm Re: Inconsistent ArcCos Behavior yehuda ben-s... 10/16/07 03:01am
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