[New-bugs-announce] [issue4139] Major error in cmath routines

[thor222]

New submission from thor222 <horizon at msbx.ws>:

There's an error in the way cmath computes the inverse sine, cosine and
tangent functions.

Example:
In 2.6: cmath.asin(2) returns 1.5707963267948966+1.3169578969248166j
However, the answer should be 1.5707963267948966-1.3169578969248166j
cmath.asin(2) returns the correct answer in 2.5.2.

Same problem exists in cmath.acos:
In 2.6: cmath.acos(2) = -1.3169578969248164j, but should be
1.3169578969248164j (once again, 2.5.2 returns the correct answer).

However, in 2.5.2 and 2.6, cmath.asin(1j) = 0.88137358701954283j, which
is correct.

----------
components: Library (Lib)
messages: 74917
nosy: thor222
severity: normal
status: open
title: Major error in cmath routines
versions: Python 2.6

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue4139>
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