Ugh. Pi pissing me off

black_mage_s · 2002-10-14T00:23:11

In the lounge, there is a topic floating around about pi and e. So I was just messsing around on my computer, and decided to make a program to calculate pi to varying degrees of accuracy. I was using this formula here: quote: to calculate pi: n/2 * sin(360/n) The larger n is, the more accurate pi is where sine is in degrees. Now, when I enter this into a calculator, using the value 2 for N, it comes out all fine and dandy, but when I threw it into my C++ program, I get all weird results. Basically, I have this for my output quote: std::cout << number/2*sin(360/number) Now, when I enter the number 2, it gives me the result 0.8128... but this isn''t the right answer, on the calculator, it said, 3.141... What giveS? http://www.big-mommas-titty-warehouse.tk unzip; strip; touch; finger; mount; fsck; more; yes; fsck; fsck; fsck; umount; sleep;

Math and Physics Programming

Started by black_mage_s October 10, 2002 03:24 PM

15 comments, last by black_mage_s 22 years, 4 months ago

Matt Calabrese

122

October 12, 2002 04:47 AM

http://mathworld.wolfram.com/PiFormulas.html

Have fun

intransigent-seal

881

October 12, 2002 06:02 AM

quote:
Original post by Divide
... use the contour (not sure if this is the right word; correct me if I''m wrong) ...

I think you mean circumference.

John B

The best thing about the internet is the way people with no experience or qualifications can pretend to be completely superior to other people who have no experience or qualifications.

googlyeyes

268

October 12, 2002 10:45 AM

and wouldn''t you need Pi to make the circle for the rope?

[edited by -

on December 25, 2002 11:41:33 PM]

Divide

122

October 12, 2002 12:22 PM

quote:
I think you mean circumference.

Thats the one I meant, thanks!

quote:
and wouldn't you need Pi to make the circle for the rope?

Nope, the idea is to measure pi. I think you'll only need to use pythagoras' rule to calculate how much rope you need [sqrt(x*x+y*y) = r], but it'll be a hell of a job

[edited by - Divide on October 12, 2002 1:46:52 PM]

Anonymous

October 12, 2002 03:36 PM

Indeed the best way to calculate PI:

   srand( time(NULL) ); int hitcircle = 0, hitoutside = 0; static const int N = 1500000; for( int curr = 0; curr < N; curr++ ) {         // Monte Carlo method, unit circle //  double x = static_cast< double >( rand() )/static_cast< double >( RAND_MAX ) * 2;  double y = static_cast< double >( rand() )/static_cast< double >( RAND_MAX ) * 2;  double dist = sqrt((x-1) * (x-1) + (y-1) * (y-1));  if( dist == 1 ) continue; // Not counted, but rare case //  if( dist < 1 ) hitcircle++;  else hitoutside++; } double PI = 4 * static_cast< double >( hitcircle )/static_cast< double >( hitcircle + hitoutside );

Bagel Man

122

October 13, 2002 11:31 PM

int A=1500000;
long double dx=1.0/A, pi=0;
for(int i=1;i{
pi+=0.5*sqrt(1.0-( i *dx)*( i *dx))*dx;
pi+=0.5*sqrt(1.0-((i+1)*dx)*((i+1)*dx))*dx;
}
pi*=4;

(I would put it in one of those code boxes, but I don''t know how)

Higher A = greater precision