const radius = size / 2;

const halfR = radius / 2;

let nLines = 0;

let nLongLines = 0;

​

function setup() {

  createCanvas(400, 400);

}

​

function draw() {

  background(220);

  fill(0);

  const xc = width>>1;

  const yc = height>>1;

  ellipse(xc, yc, 3);

​

  noFill();

  ellipse(xc, yc, size);

  const [p1,p2] = genTwoRandomPoints(xc,yc,radius);

  nLines ++;

  const d = dPoint2Line({x:xc, y:yc}, p1, p2);

  if (d <= halfR) {

    nLongLines++;

  }

​

  fill("#f00");

  ellipse(p1.x, p1.y,3);

  ellipse(p2.x, p2.y,3);

  line(p1.x,p1.y,p2.x,p2.y);

​

  text(`${nLongLines}, ${nLines}, ${nLongLines/nLines}`, 10, 20)

}

​

function genTwoRandomPoints(xc,yc,r) {

  const angle1 = random(2*PI);

  const angle2 = random(2*PI);

  const p1x = xc + r*cos(angle1);  

  const p1y = yc + r*sin(angle1);

  const p2x = xc + r*cos(angle2);  

  const p2y = yc + r*sin(angle2);

  return [{x:p1x, y:p1y}, {x:p2x, y:p2y}];

}

​

function dPoint2Line(p1, p2, p3){

  let area = Math.abs(0.5 * (p2.x * p3.y + p3.x * p1.y + p1.x * p2.y - p3.x * p2.y - p1.x * p3.y - p2.x * p1.y))    

  let bottom = sqrt((p2.x-p3.x)**2 + (p2.y-p3.y)**2);

  let height = area / bottom * 2.0;

​

  return height;

}