Opened 5 years ago
Closed 5 years ago
#90 closed defect (fixed)
(atanh -2)?
Reported by: | rtoy | Owned by: | somebody |
---|---|---|---|
Priority: | major | Milestone: | |
Component: | Core | Version: | 2013-12 |
Keywords: | Cc: |
Description
CMUCL 20e says (atanh -2) is #C(-0.54930615 -1.5707964). This is consistent with what the CLHS says about atanh for x < -1 being continuous with Quadrant III because (atanh #c(-2.0 -0.0)) is the same.
However, from the definition
atanh(z) = 1/2*(log(1+z) - log(1-z))
we have
atanh(-2) = 1/2*(log(-1) - log(3)) = 1/2*(i*pi - log(3)) = -log(3)/2 + i*pi/2
That is, the imaginary part should be positive. This would be consistent with the rule that atanh is continuous with Quadrant II.
Change History (1)
comment:1 Changed 5 years ago by toy.raymond@…
- Resolution set to fixed
- Status changed from new to closed
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commit ca2bf8c29d22aaf44caf31f1d7b6ba77ab418be5 Author: Raymond Toy <toy.raymond@…> Date: Tue Dec 24 12:57:45 2013 -0800