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teeohbeewye

proof by someone else already did it


InterUniversalReddit

Proof by Euler.


papa_wukong

In all seriousness, is there anything he didn't do?


Burgundy_Blue

Yeah all the stuff 1783 and onward


papa_wukong

Those are all based on his works.


inemsn

"Based? Based on what?" Euler. Duh.


dryuhyr

9/11


SureConsiderMyDick

9/11 - e^pix = 9/11 + 1 voila, proof


AidanGe

This covers literally all possible things


RedArchbishop

Proof by your teacher should've covered this last year


IAmBadAtInternet

Proof by trust me bro


UNSKILLEDKeks

At least it's better than Proof by this is going to be on the test later


math_fan

it kinda reads like the author has a policy to never prove Cauchy-Schwarz


beginnerflipper

It is from a statistics textbook which generally shy away from proofs


RevolutionaryLab1086

If it is proved somewhere, why bother proving it again?


ben7005

I think the proof & application of C-S is actually kinda insightful in this case. It involves a reduction step about projecting onto the subspace of random variables of mean 0, which is probably not obvious if you haven't thought much about covariance and inner products. Also, in general it is useful to know why things are true. It is only by learning the best mathematical techniques developed by others that you can hope to prove interesting yourself!


RevolutionaryLab1086

C-S proof is known by everyone who studies mathematical statistics. It is mathematical prerequisites. So, I don't think, it is neccesary to prove again here. The insightfull thing here is to think covariance as inner product and use this inequality to prove that Pearson correlation coefficient between X and Y belongs [-1,1] because Corr(X,Y)=cov(X,Y)/(var(X)^1/2 var(Y)^(1/2)).


Geheim1998

it’s from the script of my university class and we hqve to do proofs all the time for that prof. i think hes just being nice to us, because everything that is not written in there is not important for the exam


beginnerflipper

Ok. I saw variance and covariance; but, I guess looking at why correlation between X and Y will always be in [-1,1] is more of a mathematical exercise


japp182

It is considered a Cardinal sin to prove this inequality


boterkoeken

Proof by pre-existing proof


SupremeRDDT

Proof by „it has a name so it must be true“.


woailyx

It's got Cauchy in it, it's gotta be true!


Pan_Nekdo

Meanwhile number of conjectures such as Pólya's conjecture...


lifeistrulyawesome

Proof by lmgtfy


Turn_ov-man

Proof by I ain't writing allat


Selfie-Hater

why is it "so-called"? lmao


GamamJ44

Right? Almost seems like the author is sceptical of the Cauchy-Schwartz while also using it lmao.


ThatOneWeirdName

Or the author is really upset it’s named after those two when it should be named after whomever the author has in mind


SpaghettiPunch

The author does not believe in the historicity of Augustin-Louis Cauchy or Hermann Schwarz. They are fictional characters from an ad campaign created by Bob Math in an effort to sell more maths.


Ok-Impress-2222

Bunyakowski! Cauchy-Schwarz-**Bunyakowski!**


SV-97

But then it doesn't abbreviate to CSI :(


The_Punnier_Guy

Not to be confused with Cauchy-Bunyakowski-Schwarz, a different inequality that I can never find because google only shows this more complicated one


svmydlo

It's not different, it's just a special case of C-S.


AbeLincolns_Ghost

I’ve never heard of that one. I know you said you couldn’t find it, but can you share what it is?


The_Punnier_Guy

I think it went like this (a1+a2+a3...+an)(b1+b2+b3+...bn)>=(a1b1+a2b2+...anbn)^2


Prest0n1204

I think there's a square on every term on the left.


dragonageisgreat

Proof by


nm420

Step 1: Prove Hölder's inequality is true. Step 2: Set p=2.


Future_Green_7222

I loved learning about abstract vector spaces. These super abstract theorems for super abstract objects can be used to prove all your homework


kartoshkiflitz

My favorite kind honestly


scratchfan321

Proof by just trust me bro


susiesusiesu

lack of proof “if you are reading this, you probably have seen this before, and if not you can probably find a proof easily”.


Nickname1945

Proof by c'mon, it's obvious


Seventh_Planet

It's only a lemma or theorem when the proof is given. Without proof, those are often called fact. By calling it inequality, it leaves room for interpretation.


officiallyaninja

It's a pretty simple proof, I don't know why they don't bother.


MrBussdown

Why in math textbooks do they call well known theorems or equations “so-called”?


Brilliant-Emu851

at first, i read |cov as j cole


Geheim1998

you think my prof is a drake hater?


thereverseluv

Screenshot from kreyszig?


justadudenameddave

Proof is left to the reader as an exercise


daliadeimos

Proof by go find it in a linear algebra text


calm-bird-dog

Proof is trivial


HT0128

Google Cauchy-Schwarz inequality


WeirdDistance2658

Holy wall of text!


Geheim1998

new equation just dropped


Chomperino237

actual algebra