In addition to cyanoshi's post, I think these 2 videos might help you, at least for the case of 3d vectors:

https://youtu.be/eu6i7WJeinw

https://youtu.be/BaM7OCEm3G0

These 2 videos are part of a series about linear algebra.

## Search found 213 matches

- Wed Sep 28, 2016 7:11 am UTC
- Forum: Mathematics
- Topic: Vectors and Matrix Determinants
- Replies:
**3** - Views:
**2461**

- Mon Sep 26, 2016 7:42 pm UTC
- Forum: Individual XKCD Comic Threads
- Topic: 1738:"Moon Shapes"
- Replies:
**66** - Views:
**15817**

### Re: 1738:"Moon Shapes"

In the same conversation, I also learned how to know whether the moon is waxing or waning: " La lune est menteuse ". The moon is a liar: when she looks like a "D", she's waxing ( c roissante); when she looks like a "C", she's waning ( d écroissante). I always went with...

- Mon Sep 26, 2016 8:05 am UTC
- Forum: Individual XKCD Comic Threads
- Topic: 1738:"Moon Shapes"
- Replies:
**66** - Views:
**15817**

### 1738:"Moon Shapes"

http://imgs.xkcd.com/comics/moon_shapes.png Title Text: "Whenever I see a picture of the moon where the points go more than halfway around, I assume it's being eclipsed by one of those Independence Day ships and interpret the rest of the image in light of that." What about moons with face...

- Sat Sep 24, 2016 10:00 am UTC
- Forum: Mathematics
- Topic: Dataset of linear systems
- Replies:
**21** - Views:
**4888**

### Re: Dataset of linear systems

kolobisbiko wrote:I want to find the properties of a matrix is there a "tool",software for that?

I don't think matlab can provide such information.....I want 10+ properties

What properties are you talking about?

- Mon Sep 12, 2016 5:13 am UTC
- Forum: Mathematics
- Topic: Goahead52's Math Posts
- Replies:
**148** - Views:
**18648**

### Re: Goahead52's Math Posts

Goahead, the thing is that all your posts are about number theory, so there's no real "searching for subject"

And we can search post text too.

And we can search post text too.

- Fri Sep 09, 2016 9:14 am UTC
- Forum: Individual XKCD Comic Threads
- Topic: 1731: "Wrong"
- Replies:
**42** - Views:
**11189**

### Re: 1731: "Wrong"

Also when black hat guy is wrong, it's because he wants to be wrong.

- Fri Sep 09, 2016 6:46 am UTC
- Forum: Individual XKCD Comic Threads
- Topic: 1731: "Wrong"
- Replies:
**42** - Views:
**11189**

### Re: 1731: "Wrong"

Randall get out of my head. I meet too many people like him

- Wed Sep 07, 2016 3:13 am UTC
- Forum: Mathematics
- Topic: Pay to Win - a game theory problem
- Replies:
**21** - Views:
**6206**

### Re: Pay to Win - a game theory problem

Should they produce a binding contract such that they collect all the money [---] But that only works if they are allowed to do that, which I mistakenly assumed, as it wasn't written in the OP. Right, they can't do that, because neither knows how much "all the money" is. It could have bee...

- Tue Sep 06, 2016 4:03 pm UTC
- Forum: Mathematics
- Topic: Pay to Win - a game theory problem
- Replies:
**21** - Views:
**6206**

### Re: Pay to Win - a game theory problem

He could, but why would he? He doesn't know that A got more, so it's in his interest to defect. Say A got a money and B got b money. Should they produce a binding contract such that they collect all the money into one player's "bank", then they "cash out" a+b money and return ea...

- Tue Sep 06, 2016 12:33 pm UTC
- Forum: Mathematics
- Topic: Pay to Win - a game theory problem
- Replies:
**21** - Views:
**6206**

### Re: Pay to Win - a game theory problem

Well, if they can transfer before, then B could give A all the money he "got", then cooperate while A defects, giving A a+b while b still gets 0(and doesn't lose any because he only transfered the money that was allocated to him)

- Tue Sep 06, 2016 9:16 am UTC
- Forum: Mathematics
- Topic: Pay to Win - a game theory problem
- Replies:
**21** - Views:
**6206**

### Re: Pay to Win - a game theory problem

Ah, I think I have been assuming something not given, that they can transfer the money they were given BEFORE they choose to defect/cooperate. I guess I though too much about Liar Game(a psychological manga that has plenty of interesting games)

- Tue Sep 06, 2016 7:25 am UTC
- Forum: Mathematics
- Topic: Pay to Win - a game theory problem
- Replies:
**21** - Views:
**6206**

### Re: Pay to Win - a game theory problem

I'd say that in that case, the contract will be such that whatever money B gives to A, A returns that amount after A defects and B cooperates, since neither side can know the other's amount. Without a contract, A could always run off with the money. This way each side gains the money that was told t...

- Mon Sep 05, 2016 4:21 am UTC
- Forum: Mathematics
- Topic: Pay to Win - a game theory problem
- Replies:
**21** - Views:
**6206**

### Re: Pay to Win - a game theory problem

If they can talk freely, won't they just produce a contract so that one player, say A, would give all his money to B, then A cooperates and B defects, and they would share the money 50-50?

Sure B could lie about the money, but in the contract A can demand to see the piece of paper of B

Sure B could lie about the money, but in the contract A can demand to see the piece of paper of B

- Fri Sep 02, 2016 9:02 pm UTC
- Forum: Mathematics
- Topic: How to Calculate Pi without a Calculator?
- Replies:
**66** - Views:
**14191**

### Re: How to Calculate Pi without a Calculator?

In the 50?*?<=2000, and such, you can use division and 1 or 2 multiplications. It's just (a+x)*x<=b, with x a digit. I am pretty sure that x=floor(b/a)-1 (with -1 mapped to 0) will always work, but I think that x=floor(b/a) might work sometimes, so unless someone can prove otherwise, that's 2 digit...

- Fri Sep 02, 2016 2:23 pm UTC
- Forum: Mathematics
- Topic: How to Calculate Pi without a Calculator?
- Replies:
**66** - Views:
**14191**

### Re: How to Calculate Pi without a Calculator?

In the 50?*?<=2000, and such, you can use division and 1 or 2 multiplications. It's just (a+x)*x<=b, with x a digit. I am pretty sure that x=floor(b/a)-1 (with -1 mapped to 0) will always work, but I think that x=floor(b/a) might work sometimes, so unless someone can prove otherwise, that's 2 digit...

- Thu Sep 01, 2016 5:03 pm UTC
- Forum: Mathematics
- Topic: How to Calculate Pi without a Calculator?
- Replies:
**66** - Views:
**14191**

### Re: How to Calculate Pi without a Calculator?

In the 50?*?<=2000, and such, you can use division and 1 or 2 multiplications. It's just (a+x)*x<=b, with x a digit. I am pretty sure that x=floor(b/a)-1 (with -1 mapped to 0) will always work, but I think that x=floor(b/a) might work sometimes, so unless someone can prove otherwise, that's 2 digits...

- Tue Aug 30, 2016 11:32 am UTC
- Forum: Mathematics
- Topic: Goahead52's Math Posts
- Replies:
**148** - Views:
**18648**

### Re: Goahead52's Math Posts

None that I know.

- Tue Aug 30, 2016 11:14 am UTC
- Forum: Mathematics
- Topic: Goahead52's Math Posts
- Replies:
**148** - Views:
**18648**

### Re: Goahead52's Math Posts

There are infinitely many multiples of 29 not divisible by primes less than 29. A subset of these multiples is {29^k | k∈N\{0} } and that subset is countably infinite.

- Wed Aug 24, 2016 9:51 pm UTC
- Forum: Mathematics
- Topic: Goahead52's Math Posts
- Replies:
**148** - Views:
**18648**

### Re: Goahead52's Math Posts

1+9+9^2+9^3+....+9^k= 1/2* ((3^k)-1)/2)((3^k+1)+1)/2) is true for all the k`s n=((3^k)-1))/2 Sum geometric sequence is easy. I skipped that part. I had just replaced n by its value so the equation become a pure identity. It that correct? No. It is actually 1+9+9^(2)+...+9^(k)=(1/2)((3^(k+1)-1)/2)((...

- Wed Aug 24, 2016 9:44 am UTC
- Forum: Forum Games
- Topic: Random bitstream! (000zerozero000000zero)
- Replies:
**1947** - Views:
**237077**

### Re: Random bitstream! (000zerozero000000zero)

Left nostril, I am left handed... 1

- Mon Aug 22, 2016 8:24 pm UTC
- Forum: Mathematics
- Topic: Goahead52's Math Posts
- Replies:
**148** - Views:
**18648**

### Re: Goahead52's Math Posts

Please stop triple-posting. You can edit your last post if it's still the most recent post in a thread. If an identity tells you nothing about a variable, then it doesn't tell you anything useful about that variable. How do you know that the same variable could be written differently using even ext...

- Mon Aug 22, 2016 1:32 pm UTC
- Forum: Mathematics
- Topic: Goahead52's Math Posts
- Replies:
**148** - Views:
**18648**

### Re: Factorization of odd semi prime is over!

Goahead52 wrote:knowing that n=pq is odd semiprime there is a solution to :

1. approximate phi(n)=2x

2. approximate y

As we know that 2x+y=a (with a known)

1. How do you approximate phi(n) without factoring n in the first place?

2. What is y and how do you approximate it?

3. What is a?

- Sun Aug 21, 2016 12:29 pm UTC
- Forum: Logic Puzzles
- Topic: Factorial puzzle
- Replies:
**6** - Views:
**3805**

### Re: Factorial puzzle

Here are your EFN on OEIS: https://oeis.org/A002618

Also n phi(n)=phi(n^(2))

Also n phi(n)=phi(n^(2))

- Thu Aug 18, 2016 1:09 pm UTC
- Forum: Mathematics
- Topic: 1 is Not Prime
- Replies:
**17** - Views:
**5900**

### Re: 1 is Not Prime

Note that while 1 isn't a prime, 0, i and 1/e are. Otherwise you can't factorize all numbers. 1/e prime? In what context? Non-integers of course! Otherwise, how would you factorize 1/2 or π? 1/2 is simply (1/e)^{a lot}*{a lot of primes}. Okay, so maybe something breaks if you have 1=2*(1/e)^{a lot}...

- Thu Aug 18, 2016 11:43 am UTC
- Forum: Mathematics
- Topic: 1 is Not Prime
- Replies:
**17** - Views:
**5900**

### Re: 1 is Not Prime

Flumble wrote:Note that while 1 isn't a prime, 0, i and 1/e are. Otherwise you can't factorize all numbers.

1/e prime? In what context?

- Mon Aug 15, 2016 9:03 pm UTC
- Forum: Mathematics
- Topic: Misunderstanding basic math concepts, help please?
- Replies:
**338** - Views:
**78786**

### Re: Misunderstanding basic math concepts, help please?

For Twistar's question: Agree.

Other than that, all I had to say was already pointed out, and in my previous post, and it seems that treatid decided to ignore the questions I raised in that post.

Other than that, all I had to say was already pointed out, and in my previous post, and it seems that treatid decided to ignore the questions I raised in that post.

- Fri Aug 12, 2016 11:16 am UTC
- Forum: Logic Puzzles
- Topic: Sharing secret information publicly
- Replies:
**27** - Views:
**7037**

### Re: Sharing secret information publicly

If this was their solution I really think that is dumb one. A has 3 cards 1,6,7 He does not know what B has. He could write down 6 numbers : 1,2,3,5,6,7 by claiming my three cards are among those 6 cards which is true B has 3 cards : 2,3,5 He will then deduce that C holds the card 4 hence he will c...

- Tue Aug 02, 2016 7:03 pm UTC
- Forum: Mathematics
- Topic: Misunderstanding basic math concepts, help please?
- Replies:
**338** - Views:
**78786**

### Re: Misunderstanding basic math concepts, help please?

First: I have read your entire post, and most of your previous posts in this thread and the earlier threads. I am going to raise some questions and thoughts I had while reading it. Please try to answer them as clearly as you can. Also, the pertinent point is made that it really doesn't matter even i...

- Thu Jul 28, 2016 10:32 am UTC
- Forum: Mathematics
- Topic: Misunderstanding basic math concepts, help please?
- Replies:
**338** - Views:
**78786**

### Re: Misunderstanding basic math concepts, help please?

[i]{definition of 'know' here is problematic. While I don't think we can have absolute knowledge in a sense that I think axiomatic mathematics implies; I do think that we can create a complete description of the universe without needing to make any assumptions. How would you create a complete descr...

- Mon Jul 25, 2016 3:58 pm UTC
- Forum: Mathematics
- Topic: Goahead52's Math Posts
- Replies:
**148** - Views:
**18648**

### Re: Factorials

Food for thought: n!=A*B k!=B-A So n!=A(A+k!) Or A^(2)+k!A-n!=0 Solving for A: A=(-k!±sqrt(k! 2 +4n!)/2 If you want only positive A then limit it to only +. This means that k! 2 +4n! must be a perfect square, So maybe for given n you could try to find k such that k! 2 +4n! is a perfect square. This ...

- Wed Jul 20, 2016 10:46 am UTC
- Forum: Mathematics
- Topic: The liar paradox as a basis for kantian metaphysics
- Replies:
**11** - Views:
**3714**

### Re: The liar paradox as a basis for kantian metaphysics

What exactly do you mean by "x is true"? Is the empty set "true"?

- Sun Jun 05, 2016 12:07 am UTC
- Forum: Mathematics
- Topic: Misunderstanding basic math concepts, help please?
- Replies:
**338** - Views:
**78786**

### Re: Misunderstanding basic math concepts, help please?

Formal Logic Worksheet Since I started on this post, there has been further consensus for this, so I'll dive right in: 1. (~E V P) V U [prem] 2. (~E V P) ⊃ A [prem] 3. U ⊃ B [prem] 4. ~A [prem] ∴ B 5. ~(~E V P) V A [2. cond.] 6. A V ~(~E V P) [5, comm.] 7. ~A ⊃ ~(~E V P) [6, cond.] 8. ~(~E V P) ⊃ U...

- Tue May 03, 2016 4:59 pm UTC
- Forum: Mathematics
- Topic: Favorite math jokes
- Replies:
**1452** - Views:
**488582**

### Re: Favorite math jokes

Eebster the Great wrote:Surely it's a countably infinite line of mathematicians, not a line of countably infinite mathematicians. Unless each one has an unbounded number of cells or something.

They must be very dense.

- Sat Apr 02, 2016 8:41 pm UTC
- Forum: Logic Puzzles
- Topic: Drawing Two Bingo Balls
- Replies:
**3** - Views:
**3234**

### Re: Drawing Two Bingo Balls

The first solution that came to mind was this rather-inelegant one: <html><head><title>Brute Force</title> <script language="JavaScript"> function getanswer() { var a; var b; var count = 0; var sum = 0; for (a = 1; a <= 75; ++a) { for (b = 1; b <= 75; ++b) { if ...

- Wed Mar 30, 2016 5:21 pm UTC
- Forum: Logic Puzzles
- Topic: THIS IS A CHALLENGE FOR INTELLIGENT BRAINS
- Replies:
**4** - Views:
**4635**

- Thu Mar 17, 2016 10:56 am UTC
- Forum: Mathematics
- Topic: Convex problem set -- Who can solve this? I already solvedit
- Replies:
**5** - Views:
**2540**

### Re: Convex problem set -- Who can solve this? I already solv

Carlomario1990 wrote:Anyone can confirm what i do wrong in the diffferentiation part?

If i plot the graph, i get the right value, but with differentiatiton, i get the wrong value.

We can't check your work if you don't show it.

- Sat Jan 16, 2016 10:39 am UTC
- Forum: Logic Puzzles
- Topic: Escape the Frictionless Circle
- Replies:
**156** - Views:
**67060**

### Re: Escape the Frictionless Circle

Will this work? (assuming you're very strong, being in perfect health and all) 1. Pick up block, drop it on opposite side from where you picked it up from. 2. Climb over block. 3. Repeat 1 and 2. 4. Win. Would picking up the block and moving it through the vacuum to the other side cause your feet t...

- Sat Dec 26, 2015 5:12 pm UTC
- Forum: Mathematics
- Topic: difference between euler and leapfrog integrator
- Replies:
**5** - Views:
**3165**

### Re: difference between euler and leapfrog integrator

In euler integration you know the velocity as a function of position and time(v(t) as function of x(t) and t) What you do in euler intergration is choose some time interval, then assume at those intervals that velocity is constant. For each step the velocity is computed from the current time and cur...

- Mon Dec 21, 2015 4:07 am UTC
- Forum: Language/Linguistics
- Topic: Alternate Ways of Writing English
- Replies:
**9** - Views:
**6156**

### Re: Alternate Ways of Writing English

The biggest problem I have with CPG is the color coding. That's will lead to confusion among ~5% of the population, due to color vision deficiency. Instead you could use 3 colors distinct by hue, saturation and value, and have a pattern of them encode the information. Also ink is expensive, maybe ev...

- Thu Aug 20, 2015 3:59 pm UTC
- Forum: Logic Puzzles
- Topic: Who is What?
- Replies:
**21** - Views:
**4139**

### Re: Who is What?

I disagree that this is contradictory it is trivial David is the programmer born on the 31/01/1943 and Edward is the Engineer born on 01/08/1943 to the same mother and father Breaking down the facts individually 1. David and Edward are brothers [Irrelevant but creepy given the age gap] 2. {{J(D...