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/sci/ - Science & Math


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11459644 No.11459644 [Reply] [Original]

Post facts that make mathfags seethe.

I'll start

Let [math]\delta : \mathbb{R} \rightarrow \mathbb{R}[/math] such that:
[eqn]\delta (x) =
\begin{cases}
1 & x = 0 \\
0 & elsewhere
\end{cases}[/eqn]

And most importantly:

[eqn]\int\limits_{- \infty}^{+ \infty} \delta (x) dx = 1[/math]

>> No.11459647

>>11459644
Lmao I fucked up.
[eqn]\int\limits_{- \infty}^{+ \infty} \delta (x) dx = 1[/eqn]

>> No.11459650

>>11459647
What kind of integral is that?

>> No.11459653

>>11459650
A "mathfags get their panties in a bunch when they see it" kind of integral

>> No.11459657

>>11459647
why would a function defined this way make anyone seethe? it’s very useful for physics.

>> No.11459663

>>11459657
The fuck do I know. Mathfags complain about it because memesure theory or some shit

>> No.11459664

>>11459653
Can you define it in a somewhat more formal manner?

>> No.11459665

>>11459663
>Mathfags complain about it because memesure theory or some shit
what did he/she mean by this?

>> No.11459691

>>11459664
Lebesgue

>> No.11459695

>>11459691

nice definition retard

if you want to make a mathfag seethe, just claim a differential is a fraction

watch them fume while they stumble and rage mumble and their head gets redder (or browner if its a pajet)

>> No.11459704

>>11459691
But if that integral is in the Lebesgue sense, then it evaluates to zero.

>> No.11459729

>>11459664
>Formal
Fuck off with your mathfag buzzwords lmao

>> No.11459755
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11459755

>>11459644
>>11459647
Me? I prefer [eqn] \text{For real } c, \ u_c(t) \equiv \begin{cases} 1 & t > c \\ 0 & t<c \end{cases} [/eqn] then [eqn] \delta(t-c)\equiv\frac{\text{d}u_c}{\text{d}t} \ \ \text{and} \ \ \mathcal L\big \{\delta(t-c)\big\}=\exp(-cs) [/eqn]
where [math] \exp(\lambda t) [/math] is defined to be the solution of [math] x'=\lambda x, \ x_0=1 \ \ \text{for complex} \ \ \lambda [/math].

>> No.11459758

>>11459644
You absolute fucking brainlet that's literally like saying "let x=5 such that x=2"

>> No.11459761

2+2=4

>> No.11459776

>>11459644
No such function exists, so um..

>> No.11459781

>>11459776
>drives a golfball 400 yrds
Fell free to describe the force applied to the ball by the club as a function of time without [math] \delta [/math], fucking math nerd lmao

>> No.11459801

>>11459781
No such function exists, period.

>> No.11459802
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11459802

>>11459801
*pretends it exists anyway*
*gets useful results*
*shits in your mouth*

>> No.11459809

>>11459802
Then you're pretending existence of something different than what OP wrote

>> No.11459860

>>11459755
Basado

>>11459758
Lmao seethe more, mathfag

>>11459776
Seethe

>> No.11459879
File: 313 KB, 832x1080, __yagokoro_eirin_touhou_drawn_by_koyubi_littlefinger1988__7930b74a3275a45534b8a432b0f6043c.jpg [View same] [iqdb] [saucenao] [google]
11459879

>>11459644
>>11459647
>the integral of the Kronecker delta on the real line is one
>>11459776
>the Kronecker delta doesn't exist

>> No.11459900

>>11459879
Such function simply doesn't exist not because it's a distribution rather than function or whatever, but because OP fucked it up. If anything, it should say delta(0) = infinity. Joke's on him.

>> No.11459916

>>11459691
brainlet Lebesgue returns 0 to this because it is non-zero on a countable set

>> No.11460231

>>11459900
Cant you read retard?

[math]\delta (0) = 1[/math] by definition.

By the way:

[eqn]\frac{dy}{dt} = -ky \\
\frac{1}{y}dy = -kdt \\
\int \frac{1}{y} dy = -k \int dt \\
ln(y) + c_1 = -kt + c_2\\
y(t) = e^{-kt + c_2 - c_1}[/eqn]

>> No.11460241

>>11460231
>δ(0)=1
That isnt true though. Not even for engineers.

>> No.11460243

>>11459644
>>11460231
>[math]\color{green}{\delta ( 0 ) = 1}[/math]
Actual retard.

>> No.11460254

>>11460241
>>11460243
Lmao youre right, im thinking about the discrete delta function

[math]\delta [0] = 1[/math]

>> No.11460770

>>11459755
good boy, you finally learned first year differential equations

>> No.11460777

>>11460231
delta(0)=inf moron

>> No.11460798

>>11460777
Read >>11460254
You fucking imbecile faggot

>> No.11460806

>>11459801
No the Kronecker delta isn't a map between the reals.
Yes it is a function in the sense that physishits use the term.
Having a different definition of function that excludes generalized functions doesn't make you smarter just bad at communicating.

>> No.11461202
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11461202

>> No.11461341

>>11459644
>Let δ:RRδ:RR such that:
>isn't a map between the reals.

>> No.11461352

>>11459695
a differential isn't a fraction though so you're wrong and saying "lol mathfags seethe" doesn't make yo uright

>> No.11461365

>>11461352
>A differential isnt a fraction
Lmao but it is, how do you solve something like [math]\frac{dy}{dt} = -ky[/math] then faggot?

>> No.11461483
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11461483

>>11459644
*chad Russian mathematician blocks your path and pioneers distribution theory*

>> No.11461503

>>11459644
e^(t*pi*i) = cos(t) + i sin(t) isn't true for quaternions

>> No.11461552

>the heaviside distribution

>> No.11461580

>>11461365
By treating it as a fraction

>> No.11461584

>>11459644
>>11459647
Where can I go to learn the notations used here?

>> No.11461590

>>11459644
nice distribution

>> No.11461604
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11461604

>>11459663
Physicsfags complain that mathfags complain about this, but we really don't give a shit what you do.

>> No.11461613

>>11461584
A math class. None of these fags are self taught. They're all lonely math majors

>> No.11461671

>>11459695
>>11459704
>>11459916
ITT: people who missed the point of the thread

>> No.11461682

test

>> No.11461684

>>11461613
College isn't an option for me. Is there no other way? A book of notation definitions? A video?

>> No.11462451

>>11461671
>I was just pretending to be retarded

>> No.11462463

>>11461684
https://www.youtube.com/watch?v=WUvTyaaNkzM&list=PLZHQObOWTQDMsr9K-rj53DwVRMYO3t5Yr

>> No.11462720

>>11459644
calculus is like a braindrug.

>> No.11462729

>>11459695
dy/dx can be interpreted as a fraction of 1-forms in a way that's mathematically rigorous and even helpful.

>> No.11463028

>>11462729
>dy/dx can be interpreted as a fraction
Really? What field does dy belong to?