To: J3 J3/18-236
From: Anton Shterenlikht
Subject: ACOSH result value error/typo
Date: 2018-August-02
References: N2159
Introduction:
~~~~~~~~~~~~~
[340] Clause 16.9.5 ACOSH( X ) p5 Result Value has:
"If the result is complex the imaginary part
is expressed in radians and lies in the range
0 <= AIMAG (ACOSH (X)) <= {pi}".
The lower bound must be {-pi}.
For reference see e.g. DLMF, Eqn. (4.37.16):
https://dlmf.nist.gov/4.37#iv
which shows that the bounds for the imaginary
part of ACOSH are the same as for LOG,
i.e. between -pi and pi.
Edits to N2159
~~~~~~~~~~~~~~
[340] Clause 16.9.5 ACOSH( X ) p5 Result Value,
replace "0" with "{-pi}", so that the last
sentence of p5 reads as:
"If the result is complex the imaginary part
is expressed in radians and lies in the range
{-pi} <= AIMAG (ACOSH (X)) <= {pi}".
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