Archimedeen vakio

This mysterious 3.141592...,
Tämän me kaikki muistamme, vähintään seitsemän ensimmäistä desimaalia...

 π  = 3.1415926535897932384626433832795028841971693993751...
The ratio of the circumference of a circle to its diameter.

Circle-pi

 pi=C/d=C/(2r)   1)

One of Archimedes many significant contributions to mathematics was his approximation of the value of π
He was the first mathematician to establish a theoretical calculation for π instead of an estimation.
By inscribing and circumscribing polygons on a circle, he was able to constrain the value of π between 3+10/71 and 3+1/7.

 
This mysterious π 3.141592..., which comes in at every door and window, and down every chimney.
Augustus De Morgan (1806-1871)

The following tiny C code computes digits of π   (Boris Gourevitch)
      main(){
        int a=10000,b,c=8400,d,e,f[8401],g;
        for(;b-c;)f[b++]=a/5;
        for(;d=0,g=c*2;c-=14,printf("%.4d",e+d/a),e=d%a)
            for(b=c;d+=f[b]*a,f[b]=d%--g,d/=g--,--b;d*=b);
      }
    
1) Wolfram Mathworld
Jos haluat käyttää tarkempaa kaavaa: C-kielinen π arvon laskenta