When you accidentally multiply matrices the way, but nobody notices (Reddit r/mathmemes) 

New mechanic just dropped!! 196-182*0.5=7!! Most Redditors didn't get this! ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-AQiGPtbZo0I.html

You "broke" the pattern with a green pen. Black and Red alone were expected. We entered another dimension/world? Thank you for the video.

Love that "oldie but a goodie" simplification of 16 / 64.

These are the math equivalent of Dad Jokes.

It works for diagonal matrices because of all the zeros. If it works for anything else it’s a happy accident.

Bprp helped me so much by teaching me calculus and now he is teaching matrices? Huge W

In the beginning he goes "ok, so let's discuss what's going on" and i initially thought he was saying "ok, so that's disgusting" and really i agree

I love these "wrong way but not really" rules

I’m self teaching linear algebra and this video is super simple and clear to understand! I would love to see more linear algebra videos!

When you accidentally write the title of the video wrong, but nobody notices

r/mathmemes mentioned 🔥🔥

It's actually product...

Looks like a tini-mini 6th grader tried to attempt this logically 😂😂

Tomorrow is my exam i was studying matrix and determinants this notification pop up

Thank you for teaching me how to multiply matricies! I tried it with some random numbers, and it worked!

Oh gawd, I never thought others might actually multiply matrices like that. Then I realized, others probably hate matrix math that they will try to get the answer with tricks.

5:00 since regular multiplication is associative, can we add another 4 equations from multiplying matricies in reverse order (AB = BA = C, C is the wrong way)? Ok, some of them doesn't matter, but seeng AB=BA would be also invalid in general

I wish I didn’t need more of this, but I really do

Thank you

I feel like you are the Ethan Hunt of MATHEMATICS

7:56 "that's not a b it's a six" I appreciate so much that someone else experiences the deep personal horror of "whoops that letter/number/word writing sucked let me fix it" *draws literaly EXACTLY the same fucked up shape as before*

That'd be the Hadamard's which is just fine…

There's nothing wrong with multiplying the same elements in each matrix. You just get a different result than the dot product....

Thank you for helping me on calculus 2

I didn’t get how this was wrong because I was multiplying the correct way and got the same answer. Then I saw the calculation you tried in the beginning.

When it said "multiply matrices the wrong way" I did thought they meant column times row it got the right answer. Never even occured to me to lazy-multiply the entries.

Can you get all solutions for a in terms of n in a=n*sqrt(n+sqrt(a))?

doesnt matter which video, lambert w functions sure to show up

Yeah this post was cool. If we equate the formulas we get b1*c2 = 0 and c1*b2 = 0. Then our other equations inform our other required zeros. For b1 = 0: c1 = 0: (a1 or b2 = 0) & (d1 or c2 = 0) b2 = 0: c1[a2 - c2] + c2d1 = 0 For c2 = 0: c1 = 0: b1[d2 - b2] + b2a1 = 0 b2 = 0: (c1 or a2 = 0) & (b1 or d2 = 0) We were given that c1, c2 = 0. So 6(2-4) + 4*3 = 0, which is true, which is why the post fulfills the reqs. Similarly for b1, b2 = 0: c1[a2 - c2] + c2d1 = 0 Choose c2, c1, and a2 to be whatever; but then you have to calculate d1. Say c2 = 1, c1 = 2, a2 = 4. d1 = -6 X. 0. 4. 0. 2. -6. 1. Y. Can choose X and Y freely.

So if this and if that, then this. Got it. Thank you for sharing.

0:50 cursed fraction

sir rubberd the whole 7 just to cross it

It's easy to remember to dot the first row with each column on the second matrix. Then you get a number for each of those dot products. The hard part to remember is, do these numbers form a *row* or a *column* of the new matrix? I've never been able to come up with a good way to remember that, other than just memorizing it.

I always hated how matrix multiplication is taught. Rows times columns errrggh.. what? Where have I been, did I make a mistake? I always get confused. So I have devised a better method. I imagine the matrices are rotated 45 degrees to right and the result matrix is like a lego brick down between them. That determines its size. Then I imagine the numbers are like balls in a tivoli machine, just waiting to fall down to their place, just block by some imaginary obstacle. Then I release both of the obstacles at once and from both sides numbers start falling in their respecive line. And the numbers that hit each other are the ones that multiply and all the numbers that hit in the same place are added and the result is the number in that place. And then I just rotate the resulting matrix 45 degrees left and put it where math teacher wants it. I don't know if I explained it right so you can imagine it, but this is what I do in my head to prevent myself from making mistakes so I don't have to think in terms of confusing rows and columns. There is also a way to do the same thing without the 45 degree rotation, if you just imagine the right matrix is just above the left matrix but just to the right, so the resulting matrix is just right of the first and just below the second and the multiplied vectors are basically just intersections..., but the gravity thing kinda helps me... I guess I better make a video. :D Maybe one day

Looked at the thumbnail and multiplied it the correct way and did not understand what's wrong with it... Did not even occurred to me to do it that way 😂

Cool... 😊 That endin lol

just a reminder to watch the vampire matrix stand up maths video

😂😂😂😂😂. The gamma function should work here. Upper triangular matrices but very surprizing🎉

Given that the answer is correct, why would you assume the person who generated it used the wrong method?

One could also try to find examples with the dot product in the wrong order, ie. col dot row.

Element-by-element multiplication honestly feels like the most intuitive type of multiplication; I always thought that it was a bit weird how you are supposed to do that awkward row-column multiplication.

can anyone recommend a similar channel like this for other subjects too..

Just curious, why does he write the matrix multiplication like that? I'm used to writing them down in a square, where the first matrix (X) is written in the bottom left, the second matrix (Y) in the top right and the answer matrix (Z) gets into the bottom right. That way it's visually much easier to see what to multiply. Like this: |Y X|Z

Shift the right matrix up so that the resulting N*M matrix fits in the empty space. Then do dot product between the corresponding row and column vectors for each element in the result. Can't get it wrong accidentally that way.

Please explain the integral solved by RON GORDAN I am a huge fan and you explain miraculously 😊

"these aren't the same, but here's the system of equations where they are"

Hey BPRP I love your vids keep it up, I wanted to ask a question is there a way I can contact you?

l want to see bprp Solving 2017IMO p3

This one was fun..

I keep thinking I'm finally going to understand matrices but... nope.

If i am honest I thought that this was gonna be a joke on that because there is two square matrices if the same length he flipped which matrices was in front

So, are there an infinite number of matrix pairs where this sort of naive matrix multiplication works, then?

It looks like you misspelled numbers with hose underlines

Can you pls do sin(x^2)=2sinx?

doesnt this method of "multiplication" actually have a name and usage as well? i thought i remembered something really specific you can use this for

Scalar Multiplication vs Matrix Multiplication.

what is the cross product?

This stuff really reminds me of ancient greeks, chinese, and babylonian mathematicians. Its all very simple logic. But from that simplicity, we get some amazingly complex problems and solutions. Its really sucks that so much has been lost to history. Look at where we are today with just what we have saved, created, and built upon. I hope everyone here knows how special it is that we are able to gather here, and talk, and learn, and grow together.

Hello there

Integral: tan^2x ÷ (1+sec^4x ) dx ، how can you solve or just give me a hint

If I saw this video in undergrad I would have said “man everyone knows this” But now as a professor we needed AS MANY PEOPLE pointing this out possible. I could make a video EVERYDAY for the rest of my life on how to properly multiply matriciels and I will still have students multiply across on the final… you read that correctly… THE FINAL. As in after months of explaining, office hours, homework, quizzes, and tests… they still mess it up. There’s always one or two. 😢. Makes me want to quit, man.

When you do matrix multiplication, you need to also "add" another term so that to assemble the real equations. Matrix in math is just a system to solve a simultaneous equations. In other words matrix is just an isolated system made from a bunch of simultaneous equations. Consider the circle equation. y(t)=r * sin (t) x(t)=r* cos (t) But, this is only true for the first quadrant i.e when x and y is always positive. Later they find out the equation is x(t)= x * cos(t) + y * sin(t) y(t)= x * -sin(t) + y * cos(t) This is the formula for a clockwise rotation in which the rotation is in the form of a circle. From here you can isolate the equations in a matrix form. [ cos(t) sin(t) ] [ x ] [ -sin(t) cos(t) ] [ y ] So, if you try to assemble the original equation from a matrix form, you must do "addition" or you won't get the original equations.

What is this guy doing? This is not how uou multiply matrices

wow im early

Why do you call it a matrix “multiplication” when in fact it is an arbitrary rigmarole? Why don’t you just arbitrarily divide all the numbers while you are at it? 2x3=6 is a multiplication. What you are doing with those two matrices is not at all a “multiplication”.

It most definitely is how we multiply matrices. Its called the Hadamard product and its a universal basis for how modern computer architectures compute all the other matrix products hyper-efficiently. Very disingenuous video.

Let X=[(a b), (c d)] & Y=[(e f), (g h)]. Then XY=[(ae bf), (cg dh)] if any of the following cases hold: Case 1: X=0 Case 2: Y=0 Case 3: a=b=c=0 ∧ g=0 Case 4: b=c=d=0 ∧ f=0 Case 5: b=0 ∧ e=f=g=0 Case 6: c=0 ∧ f=g=h=0 Case 7: X∈Diag_2(R) ∧ Y∈Diag_2(R) Case 8: X,Y∈LT_2(R) ∧ cg=ce+dg Case 9: X,Y∈UT_2(R) ∧ bf=af+bh Cases 1 & 2 are obvious. Case 7 reflects the fact that multiplying diagonal matrices is easy, that it's componentwise for the diagonal entries. Cases 3, 4, 5, & 6 are not as obvious, but straightforward to verify. Cases 8 & 9 are interesting for only requiring two entries to be 0, such that both X & Y are upper triangular (or lower triangular) matrices, along with requiring the componentwise multiplication to hold for the entry diagonally opposite the 0 entry.

This wasn’t even the way I thought they multiplied them wrongly. I thought they had transposed the multiplication and it does indeed work that way as well. I have a feeling (but not a proof) that any 2x2 matrix multiplication that abides by your proof will also have this quality of multiplying the same way in all three ways

Just a property of triangle matrics whose application is here just

That "middle point" notation for multiplication is hell to read, just draw an "x" please.