// JavaScript Document

function PiLeibniz(size){
var x=0;
for (var i=2; i<=size; i=i+4){
x=x+((1/(i-1))-(1/(i+1)));
}
x=x*4;
return x;
}

function PiWallis(size){
var x=1;
for (var i=2; i<=size; i=i+2){
x=x*(i/(i-1))*(i/(i+1));
}
x=x*2;
return x;
}

function PiBasel(size){
var x=0;
for (var i=1; i<=size; i=i+1){
x=x+(1/(i*i));
}
x=x*6;
x=Math.sqrt(x);
return x;
}

function PiEuler(size){
var x=0;
for (var i=1; i<=size; i=i+1){
x=x+(1/Math.pow(i,4));
}
x=x*90;
x=Math.pow(x,(1/4));
return x;
}

function PiEuler1(){
var x = 1/7;
var y = 3/79;
//alert("x: "+x+" y: "+y);
x = Math.atan(x);
y = Math.atan(y);
//alert("x: "+x+" y: "+y);
var z = (20*x) - (8*y);
//alert("z: "+z);
return z;
}

function PiMachin(){
var x = 1/5;
var y = 1/239;
x = Math.atan(x);
y = Math.atan(y);
var z = (4*x) - (y);
z=z*4;
return (z);
}

function Nepero(n){
var x=1;
var fact=1;
for(var i=1; i<=n; i++){
fact=1;
//alert("i: "+i);
for(var q=i; q>=1; q=q-1){
fact=fact*q;
//alert("Fact: "+fact);
}
x=x+(1/fact);
//alert("x: "+x);
}
//alert(x);
return(x);
}

function NeperoR(N){
if(N==0) return(1);
else{
  Nepe = (1+(1/N)*NeperoR(N-1));
  return (Nepe);
}
}

var piMath = Math.PI()
var piWall = PiWallis(20);

var difference = abs(piMath - piWall);