|Reported by:||rtoy||Owned by:||somebody|
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))
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.