[Numpy-discussion] numpy.arcsin of complex number... strange

Travis Oliphant oliphant.travis at ieee.org
Mon Jul 31 16:57:55 CDT 2006


Daniel Poitras wrote:
> Hello,
>
> I tried different arcsin functions on a complex number (z=0.52+0j) and obtained
> the following results:
>
> cmath.asin(z) gives (0.54685095069594414+0j) #okay
>
> -1j*log(1j*z+sqrt(1-z**2)) gives (0.54685095069594414+0j) #okay, by definition
>
> numarray.arcsin(z) gives (0.54685095069594414+0j) #still okay
>
> but
>
> numpy.arcsin(z) gives (0.54685095069594414+0.54685095069594414j) #bug??
>
>
> Is it really a bug in numpy, or is there another explanation?
>   

It's a bug.   I seem to remember fixing this one before, but I guess it 
crept back in (or the bug I fixed was a similar one in another piece of 
code.    Should be fixed in SVN now.

-Travis





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