Matrices

wolfram alpha

>>8964696
yea that is gonna help me on an exam. I need a faster way so I don't waste time on 1 fucking question.

>>8964708
>yea that is gonna help me on an exam.
you don't own a phone?

> I need a faster way so I don't waste time on 1 fucking question.
what's wrong with RREFing the matrix and the identity at the same time?

>>8964712
>using a phone during an exam
Please tell me what uni you go to that allows this.

>>8964693
>How can I find the inverse of a matrix without fucking with the identity
GAUS
A
U
S

(And I am not even kidding https://en.wikipedia.org/wiki/Gaussian_elimination)
That is probably the best you can get. There are other algorithms but they are all more complicated.

>>8964726
>Please tell me what uni you go to that allows this.
harvard

By hand you're not going to find a faster way than RREF. Nothing on an exam should take too long if you know what you're doing.

>>8964740
I think Gauss is precisely what he meant by 'fucking with the identity'

>>8964693
"Fucking with the identity" is the same thing as computing the inverse of 2 by doing 1/2 (1 is the identity for real numbers). It's just an abstraction of that and there is no way around it (without getting obscure)

>>8964760
Yes, but it is an algorithm, there should be no fucking around, just computing.
I thought that OP may not have understood correctly (or completely) how the algorithm works, it is just training (very boring training) to do it fast.

And aside from Gauß there isn't so much more that you can easily do in your head...

If it's 3X3 cofactor method is the best. For higher order matrix, its more straightforward but more time consuming, however, if yoy are quick at arithmetic, you can get it to work for 4x4, but you have to compute 16 3x3 determinats and a 4x4 one, so idk if it will work for ypu.

>>8964775
>Gauß
>ß
Did you really need to use the german letter just to say Gauss?

>>8964693
>studying a level of Linear Algebra where you're being made to perform stupid computations a monkey could do instead of proving shit
What's it like to be a brainlet?

>>8964931
Just because my brain is as small as your penis doesn't mean you can bully me.

>>8964693
Fastest method is cofactors, obviously. It reduces the problem into simply computing determinants and determinants are so fucking easy to compute.

You can, with some training, compute 3x3 determinants in your head and for those trickier ones with some algebraic manipulations you can simplify the determinant and then calculate it mentally in less than a second. Literally determinants are the chillest things in the world because there is no end to how much you can simplify them. Just fucking do it.

I really do not understand why books don't teach this method. I remember I learned linear algebra (all the way to eigenvalues and eigenvectors) from a book I got myself after I finished high school and the only method I was taught was the one you are talking about.

Then I took a linear algebra course in university and out of nowhere the fucking madman professor tells me you can compute inverses just using determinants and not only that, but other than the classical way of computing determinants, if you learn the algebraic properties of determinants (something my fucking book didn't cover for some reason) then you can compute them at the speed of light.

Cramer's Rule

>>8964957

my class in linear algebra 1 (math 321) was in a computer lab. so there was big ass desktops in between everyone and the teacher.

pull out phone -> wolfram alpha matrix -> get all info on it within 1 minute

they werent easy 3x3 matrix either, crazy stuff with equations in them and sometimes complex numbers

>>8964961
brainlet tier method

how big are these matrices?

>>8964923
>Did you really need to use the german letter just to say Gauss?
Yes.

Writing Gauss in German is his wrong name and sounds different.

Writing augmented matrix with identity on the right and then doing row reduction until you got identity on the left is pretty much the fastest method, using cofactor matrices requires calculating shitload of determinants, calculating which is tedious, especially for matrices 4x4 or bigger.
You may want to check out inverting block matrices, which sometimes may be faster, especially with bigger matrices that have zero blocks

>>8964708
How shitty is your school if you have to explicitly give the inverse and not just check if matrix is invertible and write [math]A^{-1}[/math] when needed?

>>8964693
let me check my process simulation notes.

try looking up the newton rhapson method.

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Not scanning. If you know this list you either gauss eliminate or not.

/thread

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>>8964775
>spelling gauss that way

holy shit what a faggot hahahahahahahahahahahahahahahahahahahahahahahahahaha

>>8965768
It is his name.
Spelling him any other way is wrong and shows that you have no clue about his name.
Its like calling Galois "gahloihs" a murder of the french language.

The ß is also a special German character spelling it any other way will change how is name sounds, the ß is a hard and has a different sound then the ss (not be confused with the SS).

>>8964749
wtf I hate harvard now

>>8964693
The augmented identity matrix is the best method for larger matrices. Using shit like the adjoint method or block mult. is JUST-tier.

>>8964693
https://en.wikipedia.org/wiki/Adjugate_matrix

>>8964693
are you saying gaussian elimination is too much for you to handle?

>>8965784
German here we mostly use 'ss' when online or in sms

>>8964693
Cramer's Rule

>>8964775
lmao, everyone get a load of this guy

>>8965887
??

>>8965865
>we
No, only uneducated retards (most of them sandniggers who don't give a fuck about the language) do that.

>sms
In which century are you living grandpa?

>>8966071
>>8965865
>germans on my /sci/
REEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE!!!!!!!!!!!!!!!1

>>8964693
Cramer rule is the fastest method, you need to practice how to calculate determinants anyway

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>>8964775
I spell it GauB desu

>>8965721
Are any of us speaking German you dweeb?

>>8964923
Did you really need to make this post?

>>8966458
I do and Gauß is the correct name. The other german anon is just doing it correctly. Don't be mad.

>>8966345
>>8966486
>the eternal kraut

>>8966486
The Esset and ss are the same. A lot of contemporary German lira ture doesn't even use the esset anymore