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/sci/ - Science & Math

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4165519 No.4165519 [Reply] [Original]

"infinity" × 0 isn't defined.

Am I right about that, mathfriends?

>> No.4165526

You are right about that.

>> No.4165536
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4165536

better still be zero or all of math enrages me. infinity divided by zero is undefined but muliplying it should still be zero. I swear if mathematicians changed this on me i'm gonna bust some skulls.

>> No.4165539

>>4165526
So, "infinity" × n is "infinity for n >= 1, -"infinity" for n =< -1 and 0 for 0 < n < 1 and -1 < n < 0.

Still correct?

>> No.4165540

No, it is zero.

ZERO

>> No.4165542

>>4165536
lim x * 1/x = lim(x) * lim(1/x)
as x-> inf, we get 0 * inf. But in this case lim (x*1/x) = lim(x/x) = lim(1) = 1.

>> No.4165541

"infinity" x 0 = 0

Because when there is none of infinity, there is none of fucking infinity.

>> No.4165543

>>4165536
> infinity divided by zero is undefined
The hell? It's infinity.

>> No.4165544

>>4165539
You're not dealing with numbers here, but with limits.
Read up on the topic (in case you're not trolling).

>> No.4165546

Infinity is not a member of R.
/thread

>> No.4165547

>>4165542
Good job, you calculated that the limit of 1 is 1.

>> No.4165549

>>4165543
Anything divided by zero is undefined.

>> No.4165551

>>4165546
It s a member of expanded R.

>> No.4165552

Infinity isn't a number and isn't considered an element of any of the rings, fields, integral domains etc you're thinking of, so the axioms and theorems don't necessarily work on it (One of which is a0=0a=0).

>> No.4165553
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4165553

>>4165542
>>4165542
that's not the same as 0*inf at all

0*inf makes no mathematical sense, so I think it's somewhat fair to call it undefined.

"syntax error" would probably be closer to the mark though.

>> No.4165556

>>4165541
>>4165541
>>4165541
>>4165541
/thread

>> No.4165558

Zero infinities are INFINITY!!!1

>> No.4165567

>>4165547
I was showing that if f(x) -> inf, and g(x) -> 0.
Then f(x)g(x) -> To anything

>> No.4165572

>>4165551
field axioms don't hold

>> No.4165582

http://www.wolframalpha.com/input/?i=0*Infinity

ie. it depends on the rules of the field yo're in

>> No.4165590
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4165590

"infinity" × 0 = 0

>> No.4165605
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4165605

>>4165590
0 * infinity is not defined

>> No.4165621
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4165621

>>4165605
>>4165590

>> No.4166185

>>4165519

provide a definition of infinity.

>> No.4166189

∞*0 = chicken

>>4165519
It is now, bitch.

>> No.4166190

Multiplication is an operation defined on the integers, rationals, reals or complex numbers. It isn't defined in a consistent way on any set including infinity.

>> No.4166204

>>4166190 Multiplication is an operation defined on the integers, rationals, reals or complex numbers.
Any any other set where you call some operation multiplication since it seems convenient. Functions, vectors, extended reals, ...

>> No.4166211

>implying ∞ is a number

>> No.4166214

Infinity is a concept. Not a number.

There is nothing truly infinite in the universe.

>> No.4166222

I tend to view infinity as an arbitrarily large number, and 0 as an arbitrarily small one. So for me,0*infinity=0 just as for any other number. On the other hand, any number times infinity equals infinity...

>> No.4166226

>>4166214
1 is a concept. Not a number.
There is nothing truly 1 in the universe.

>> No.4166243

>>4166226
And what is your purpose on this board? Being a gigantic tripfag troll?

>> No.4166246

>>4166226
Aren't you supposed to post some advanced physics stuff that I don't understand instead of trolling?

>> No.4166250

>>4166246
>>4166243
>implying he's not right

>> No.4166255

>>4166246

>GL talking down others for posting useless garbage

>> No.4166264

>>4166255
I lack the education to post cool physics knowledge, but Josef can do it.

>> No.4166266

>>4166214
>nothing infinite in nature

What about singularities?
>owait this makes my argument circular

>> No.4166269

>>4166264

you lack the education to make a lot of the statements you do in some of these threads... You still do so despite

>> No.4166275

>>4166226
Time
Empty space

>> No.4166278

<span class="math">\infty[/spoiler] isn't any more or less of a concept than anything else you take from math, only that you can apply the concept of (small) finite numbers much more often in real life. However, when's the last time you applied <span class="math">\sqrt{7+e}[/spoiler]? Never? Does that make it less of a number, less of a real thing (no pun intended)? In fact, you've never experienced the number 1 in life, it's a convenient way of describing something there's no multitude of, sure, but from using 1 you immediately deduct that another 1 would make 2 of them, (again!) intuitively applying the mathematics you've dealt with for years. <span class="math">\infty[/spoiler] isn't any different in that context, only that it doesn't occur when shopping for groceries, but just because the dark side of the moon doesn't appear in real life that doesn't make it non-existent.

(I've used "exists" in the mathematical sense here, not commenting on the philosophical difficulties.)

>> No.4166280

>>4166269
>you lack the education
>anonymous

ok

>> No.4166281

>>4166269
That's right. I'm learning from being corrected.

>> No.4166287

Everything in nature is infinite yet renormalizable.
/thread

>> No.4166289

>>4166278
>>4166278
Nice argument, of course, difficulties with brisking away identity metaphysics, but never the less.

>> No.4166306

Infinity and non-constructive choice are made-up bullshit. If you are not an ultrafinitist you're just practicing a cult religion.

>> No.4166322

>>4166306
>2011
>not formalist
ISHYGDDT

>> No.4166331

>>4166322
Just because semantics is hard doesn't mean we throw it away.

>> No.4166332

It's undefinied faggots, just like 1 to the infinity is undefinied.

>> No.4166338

>>4166322
Formalism still takes blade to epistemological problems, though.

>> No.4166350
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4166350

>> No.4166355

the number that comest closest to a definition is 0/0 (zero devided by zero)

>> No.4166379

>>4166331
Being formalist doesn't mean you throw out semantics. It means your semantics are fixed by the axioms that are used, and not by the existance of an ideal object (platonist), nor by the construction of an object (constructivist).

>> No.4166381

Infinity isn't a number. This is an indeterminate form. In fields where there are infinite elements, like the surreals, it is 0. In limits with a product, one part going to infinity and the other to 0, it's indeterminate.

>> No.4166384

>>4166379
Formalism as in philosophy-of-math stuff is indeed the rejection of semantics.

>> No.4166407

>>4166384
As a formalist, I took semantics to mean formal semantics. You define the axioms (the rules of the game), and look at the statements that are consequences of those axioms. The semantics is collection of statements that are consequences of the axioms.
Now, how this applies to the relation between mathemetics and the real world is: "Hey, if I pick my rules like this, my formal objects behave similar to physical objects. I guess I'll use these rules to describe those physical objects!". However, formalists reject the notion that the formal objects are an ideal form of a physical object (whatever that really means).

>> No.4166410

>2011
>giving a shit

>> No.4166411

>>4166407
that is not what 'semantics' means.

>> No.4166414

>>4166411
That is what it means to a formalist.
I know that Platonists mean something different with it.
Deal with it.

>> No.4166421

>>4166414
It means the same thing to formalists. They just don't think it applies.

I can agree on a definition of god even though I don't think god exists. Some day, perhaps you will appreciate things like this.

>> No.4166443

>>4166421
I think you've got yourself stuck in a paradox there, guy.

>> No.4166447

Lim x→inf F(x) = 0x

Nope, its a straight line along the x axis. Zero times infinity is zero.

>> No.4166449

>>4166447
... and this is what happens when biologists try math.

>> No.4166506

>>4166449
Tru dat.
That nigger has no knowledge of math from what I noticed.
I can do the same thing to 'prove' that infinity*0 equals 1.
Lim x->infinity of (1/x)*x since 1/x approaches 0 when it approaches infinity and x approaches infinity when it approaches infinity.
Lim x->infinity (1/x)*x = lim x-> infinity 1=1
That guy's logic: 0*infinity=1

>> No.4166525

>>4165536
>Check out these cool drawings I made during my college algebra class, while we're on the subject of math, /sci/.

>> No.4166552

Inifinity is the word maths use when numbers run out. Its not a perfect language, nothing ever is.

>> No.4166564

Read L'Hôpital's rule
http://en.wikipedia.org/wiki/L%27H%C3%B4pital%27s_rule

>> No.4166581

In some situations (like measure theory) one defines 0*infty=0, in other situations like analysis 0*infty can take different values, in again other situations like when dealing with Möbius transformations 0*infty=infty.

>> No.4166586

>>4166581
>implying measure theory is not analysis

>> No.4166617

X*Y.
X = 0, Y = lim -> infinity
X*Y = 0

X*Y
X = lim x -> 0
X*Y = +-infinity

This is why it is indeterminate.

>> No.4166626

>>4166617
Second y is infinity

>> No.4166659

>>4166586
Oh shut up. With infinities in measure theory I obviously meant the calculus that's defined for the values measures take and with infinities in analysis I very obviously meant in terms of limits. All you're being is an obnoxious retard.

>> No.4166674
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4166674

<div class="math">\infty \cdot 0 = -1</div>

>> No.4166682

>>4166674
Derivative/gradient of a line is zero. Nice try.

>> No.4166689

>>4166682
What the actual fuck. I click on /sci/ and this is the first thing I read.

>> No.4166694

Who the fuck says gradient instead of slope?

>People who haven't studied multivariable calculus.

>> No.4166695

>>4166682
Time to all quote this post along reaction images.

Or not. But still, damn.

>> No.4166706
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4166706

>>4166682

>> No.4168269

>>4166674
/thread

>> No.4168276

In physics, we make it approximately infinite or approximately zero according to which largest/smallest order of magnitude.