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Re: Very strange behaviour of ArcTan[]

• To: mathgroup at smc.vnet.net
• Subject: [mg102669] Re: [mg102656] Very strange behaviour of ArcTan[]
• From: DrMajorBob <btreat1 at austin.rr.com>
• Date: Tue, 18 Aug 2009 06:08:16 -0400 (EDT)
• References: <200908171206.IAA06945@smc.vnet.net>
• Reply-to: drmajorbob at bigfoot.com

Nothing wrong there at all.

t = ArcTan[0.5, $MachinePrecision]
Tan@t == $MachinePrecision/0.5

1.53947

True

u = ArcTan[0.5]
Tan@u == 0.5

0.463648

True

That's exactly what's supposed to happen.

Bobby

On Mon, 17 Aug 2009 07:06:56 -0500, 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?
>



-- 
DrMajorBob at bigfoot.com

• References:
  • Very strange behaviour of ArcTan[]
    • From: Alexey <lehin.p@gmail.com>