       Re: DiracDelta Function question

• To: mathgroup at smc.vnet.net
• Subject: [mg21329] Re: DiracDelta Function question
• From: "Gregor" <governey at duckman.sid.hp.com>
• Date: Fri, 24 Dec 1999 03:42:31 -0500 (EST)
• Organization: SSO-IT, Hewlett-Packard Co.
• References: <831vk0\$g89@smc.vnet.net> <83aare\$qq0@smc.vnet.net> <83ncod\$6ed\$3@dragonfly.wolfram.com>
• Sender: owner-wri-mathgroup at wolfram.com

```It appears to be a bug with Mathematica 4 on NT4 SP6a. It should calculate also the
first input. Both are 1/2 (at least using a pencil and paper).

In:=
Integrate[DiracDelta[2 x - 1], {x, -Infinity, +Infinity}]

Out=
\!\(\*
RowBox[{
SubsuperscriptBox["\[Integral]",
InterpretationBox[\(-\[Infinity]\),
DirectedInfinity[ -1]],
InterpretationBox["\[Infinity]",

ectedInfinity[
1]]], \(DiracDelta[\(-1\) + 2\ x] \[DifferentialD]x\)}]\)

In:=
Integrate[DiracDelta[2 x - 2], {x, -Infinity, +Infinity}]

Out=
\!\(1\/2\)

John M. Jowett wrote in message <83ncod\$6ed\$3 at dragonfly.wolfram.com>...
>
>
>Bojan Bistrovic wrote:
>>
>> Julian Francis wrote:
>> > Why is mathematica unable to evaluate:
>> > Integrate[DiracDelta[2 x - 1], {x, -Infinity, +Infinity}]
>> >
>> > Also interestingly:
>> > Integrate[DiracDelta[2 x - 2], {x, -Infinity, +Infinity}]
>> >
>> > returns (1/2)
>> >
>> > I should have thought that the answer in both cases would be 1.
>>>>>>>>>> SNIP <<<<<<<<<<<<<
>> It's probably a bug in MS-Windows :-). My Linux version returns 1/2 in
>
>On my Windows (NT) system, Mathematica 4.0 returns 1/2, quite correctly,
>for both cases.  (The first one may have taken a few seconds longer
>while Mathematica loaded something behind the scenes.)
>
>John Jowett
>
>
>

```

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