function getPositions (count, r = 50, angle = 0, x0 = r, y0 = r) {
  let pos = []
  let step = 360 / count
  for (let i = 0; i < count; i++) {
    pos.push(getAngle(r, step * i + angle, x0, y0))
  }
  return pos
}
@param {count} point's count
@param {r} radius
@param {angle} init angle
@param {x0} center point x
@param {y0} center point y