var y1, y2, y3;

​

function setup() {

  createCanvas(600, 600);

  initPoints();

}

​

function draw() {

  background(166, 166, 255);

  fill("pink");

  noStroke();

  triangle(x1, y1, x2, y2, x3, y3);

  noStroke();

  fill(255);

  ellipse(x1, y1, 10, 10);

  ellipse(x2, y2, 10, 10);

  ellipse(x3, y3, 10, 10);

  var ma = (y2 - y1) / (x2 - x1);

  var mb = (y3 - y2) / (x3 - x2);

  var cx = ((ma * mb * (y1 - y3)) + (mb * (x1 + x2)) - (ma * (x2 + x3))) / (2 * (mb - ma));

  var cy = -1*(cx-(x1+x2)/2) /ma + ((y1+y2)/2);

  var dx = x1 - cx;

  var dy = y1 - cy;

  var radius = sqrt(dx*dx + dy*dy);

  noFill();

  strokeWeight(2);

  stroke(255);

  ellipse(cx, cy, radius*2, radius*2);

  fill(255);

  ellipse(cx, cy, 15);

}

​

function mousePressed() {

  initPoints();

}

​

function initPoints() {

  x1 = width * random(0.2, 0.8);

  x2 = width * random(0.2, 0.8);

  x3 = width * random(0.2, 0.8);

  y1 = height * random(0.2, 0.8);

  y2 = height * random(0.2, 0.8);

  y3 = height * random(0.2, 0.8);

}