const threePointAngle = Fig.threePointAngle;
const getPoint = Fig.getPoint;
const p1 = threePointAngle(getPoint([1, 0]), getPoint([0, 0]), getPoint([0, 1]));
console.log(p1);
// 1.5707963267948966
const p2 = threePointAngle(getPoint([0, 1]), getPoint([0, 0]), getPoint([1, 0]));
console.log(p2);
// 4.71238898038469
Returns the angle from the line (p1, p2) to the line (p1, p3) in the positive rotation direction and normalized from 0 to Math.PI * 2.