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Re: Very strange behaviour of ArcTan[]

• To: mathgroup at smc.vnet.net
• Subject: [mg102672] Re: [mg102656] Very strange behaviour of ArcTan[]
• From: Bob Hanlon <hanlonr at cox.net>
• Date: Tue, 18 Aug 2009 06:08:48 -0400 (EDT)
• Reply-to: hanlonr at cox.net

$MachinePrecision is an integer (16 on my machine). Perhaps you meant to use ArcTan[0.5 + $MachineEpsilon]?


Bob Hanlon

---- Alexey <lehin.p at gmail.com> wrote: 

=============
Hello,
I just have discovered some strange (buggy?) feature of ArcTan[]
function in Mathematica 5.2. Try the following;

In[72]:=
ArcTan[.5,$MachinePrecision]
ArcTan[.5]

Out[72]=
1.53947

Out[73]=
0.463648

The expression ArcTan[.5,$MachinePrecision] must (?) give an error but
in really gives some strange output without any error messages... What
do you think about this?