[Numpy-discussion] numpy.arcsin strange behavior?

Poitras, Daniel Daniel.Poitras at nrc-cnrc.gc.ca
Fri Jul 28 15:07:24 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 a bug in numpy, or is there another explanation? 
 
Thanks 
 
Daniel Poitras 
Ottawa


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