## Search found 16 matches

Sun Feb 17, 2008 9:28 pm UTC
Forum: Mathematics
Topic: Quick help solving a simple equation?
Replies: 9
Views: 1689

### Re: Quick help solving a simple equation?

V2*sin(theta) - V1*d = d2*cos(theta)
V2*sin(th)-V1*d=d2*sqrt(1-sin(th)^2)
V2^2*sin(th)^2-2*V1*V2*d*sin(th)+(V1*d)^2=d2^2-d2^2*sin(th)^2
sin(th)=x; th=arcsin(x)

(V2^2+d2^2)*x^2-2*V1*V2*d*x+(V1*d)^2-d2^2=0

And now you solve the quadratic equation.
Sun Feb 10, 2008 4:47 pm UTC
Forum: Mathematics
Topic: How do they find big primes?
Replies: 19
Views: 3212

### Re: How do they find big primes?

Guess and check. With pencil and paper.

No calculators.

That sounds really fun.

I checked the wikipedia link and it lists some deterministic tests but gives no explanation on how or why they work.
Sun Feb 10, 2008 3:54 pm UTC
Forum: Mathematics
Topic: How do they find big primes?
Replies: 19
Views: 3212

### How do they find big primes?

I have been thinking about this, how do you prove that something like 2^32582657-1 is a prime number? I know about Miller-Rabin and similar probabilistic algorithms but they don't really prove if a number is prime or not, just that it's likely enough so that you can use it for encryption or somethin...
Fri Jan 18, 2008 2:36 pm UTC
Forum: Coding
Topic: How many programming languages do you know?
Replies: 119
Views: 36277

### Re: How many programming languages do you know?

C
Java
Prolog
C++
C#
SQL
ARM assembly
Wed Jan 16, 2008 10:52 pm UTC
Forum: Science
Topic: Dimensionality of gravity
Replies: 24
Views: 2766

### Re: Dimensionality of gravity

I read most of the posts here but this doesn't quite make sense to me. When I solve the equation and let the speed equal c this is what I get. (dx/dT)^2+(dy/dT)^2+(dz/dT)^2-(c*(dt/dT))^2 = -c^2 v=sqrt((dx/dT)^2+(dy/dT)^2+(dz/dT)^2)=c c^2-(c*(dt/dT))^2=-c^2 -c^2*(dt/dT)^2=-2*c^2 (dt/dT)^2=2 dt/dT=sqr...
Tue Jan 15, 2008 11:16 pm UTC
Forum: Mathematics
Topic: Mathematical Busking
Replies: 50
Views: 5085

### Re: Mathematical Busking

Sat Dec 22, 2007 4:25 pm UTC
Forum: Computer Science
Topic: AI and checkers
Replies: 18
Views: 6389

### Re: AI and checkers

To answer some of the questions, I'm doing this for fun and as an exercise in AI. This semester is boring and I wanted to do something other then spend 5 hours trying to figure out why my program compiled on Fendora generates floating point exception on Devil. Since this is my first try in AI I wont...
Thu Dec 20, 2007 6:31 pm UTC
Forum: Computer Science
Topic: AI and checkers
Replies: 18
Views: 6389

### Re: AI and checkers

Maybe zmljuk can do it better. I plan to. Seriously, I'm already using minmax algorithm for finding the best move with looking 4 moves ahead. Alpha pruning sounds like a good idea, I'll try that. I don't know anything about neural networks so backpropagation a little too much for now and I never re...
Wed Dec 19, 2007 1:51 pm UTC
Forum: Computer Science
Topic: AI and checkers
Replies: 18
Views: 6389

### AI and checkers

Hi, I am making a computer program that plays checkers. So far it just checks all possible combinations for the next 4 moves and selects the best one assuming the opponent doesn't make mistakes. It also has 2 files with precomputed moves. One for the first 8 moves and one for end game(when 6 pieces ...
Wed Nov 28, 2007 9:21 pm UTC
Forum: Mathematics
Topic: What proofs are (split from amusing test answers)
Replies: 37
Views: 4038

### Re: What proofs are (split from amusing test answers)

I've seen people make statements that are slightly different than the statement you are quoting. But not once did anyone say the words "always true" as far as I can find. OK I made up the quote, and it's actually very very wrong. But you still can't apply modus ponens to it self, you have...
Wed Nov 28, 2007 8:36 pm UTC
Forum: Mathematics
Topic: What proofs are (split from amusing test answers)
Replies: 37
Views: 4038

### Re: What proofs are (split from amusing test answers)

..."if Y is true, then X is true" is always true...

Doesn't the tortoise and Achilles story point out this is wrong. You can't use "if X then Y" statements without modus ponens. And you can't apply modus ponens to it self so you have to except at least something a priory.
Sun Nov 25, 2007 9:23 pm UTC
Forum: Coding
Topic: RSA
Replies: 3
Views: 1449

### Re: RSA

Thanks, that clears it up.
Sun Nov 25, 2007 1:32 pm UTC
Forum: Coding
Topic: RSA
Replies: 3
Views: 1449

### RSA

We learned about RSA algorithm recently. For homework I programed my version using gmp.h and it's actually working. The thing is I still don't understand why it's working. Could someone explain to me why does C=(M^e mod n) => M=(C^d mod n). No one explained to me how come these functions are inverse...
Mon Nov 19, 2007 12:12 am UTC
Forum: Coding
Topic: ideas for an algorithm
Replies: 2
Views: 1457

### Re: ideas for an algorithm

As I understand it, it may not be possible to fill the requirements. The easiest example I can think with your same values of d=3, s=4, r=6 is:

a = b = c = e = f = 12
g = h = i = j = 3

What do you do then?

Then you get an error message and the user can change the parameters.
Sun Nov 18, 2007 4:16 pm UTC
Forum: Coding
Topic: ideas for an algorithm
Replies: 2
Views: 1457

### ideas for an algorithm

I have a programing problem and can't think of any way to even begin solving it. Consider a char matrix with d*s rows and r columns. It is filled with number a of 'A' characters, number b of 'B' characters and so on in such a way that each character can appear only once in each row. This means that ...
Thu Nov 15, 2007 11:00 am UTC
Forum: General
Topic: Who the dickens are you?
Replies: 10922
Views: 2421974

### Re: POST HERE FIRST - INTRO THREAD THE THIRD

Hi I'm Zmljuk. I like xkcd comics so I thought I'd register.

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