[SciPy-user] numpy 1.0b1: arccosh(0.0)

David Cournapeau david at ar.media.kyoto-u.ac.jp
Fri Aug 4 06:35:18 CDT 2006


Pierre SCHNIZER wrote:
> Hello,
>
> 	I don't know if that only happens on my machine....
> For numpy 1.0 b1 I get
>
> <snip>
> In [241]:numpy.arccosh(0)
> Out[241]:nan
I get the same results, but this is logical... acosh is defined by 
0.5(exp(z) + exp(-z)) for z complex, and this cannot be smaller than 1 
for z real, and never equal to 0, so arccosh(0) does not really make 
sense to me,

cheers,

David


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