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

Daniel Poitras daniel.poitras at nrc.ca
Fri Jul 28 13:14:51 CDT 2006


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?


Thanks

Daniel Poitras
Ottawa





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