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help / color / mirror / Atom feedFrom: Tom Lane <tgl@sss.pgh.pa.us>
To: Max Lipsky <maxlipsky@gmail.com>
Cc: pgsql-sql@lists.postgresql.org
Subject: Re: Problem in
Date: Thu, 25 Apr 2019 12:56:46 -0400
Message-ID: <26108.1556211406@sss.pgh.pa.us> (raw)
In-Reply-To: <2164C531-EAA3-4CAF-996F-FEB0E5F73B32@gmail.com>
References: <2164C531-EAA3-4CAF-996F-FEB0E5F73B32@gmail.com>
Max Lipsky <maxlipsky@gmail.com> writes:
> SELECT acos(
> cos(radians(48.9193))
> * cos(radians(48.9193))
> * cos(radians(2.5431) - radians(2.5431))
> + sin(radians(48.9193))
> * sin(radians(48.9193))
> ) as result;
> This returned [22003] ERROR: input is out of range
Not too surprising, because (at least on my machine)
regression=# select cos(radians(48.9193))
regression-# * cos(radians(48.9193)) + sin(radians(48.9193))
regression-# * sin(radians(48.9193));
?column?
--------------------
1.0000000000000002
(1 row)
Problems of this sort are inevitable when working with finite-precision
math.
https://en.wikipedia.org/wiki/Round-off_error
regards, tom lane
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To: pgsql-sql@postgresql.org
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Subject: Re: Problem in
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