Re: Problem in

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Max Lipsky <maxlipsky(at)gmail(dot)com>
Cc: pgsql-sql(at)lists(dot)postgresql(dot)org
Subject: Re: Problem in
Date: 2019-04-25 16:56:46
Message-ID: 26108.1556211406@sss.pgh.pa.us
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Max Lipsky <maxlipsky(at)gmail(dot)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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  • Problem in at 2019-04-25 13:45:18 from Max Lipsky

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