Calculating triangles

triangle.js

// http://www.teacherschoice.com.au/Maths_Library/Trigonometry/triangle_given_3_points.htm
const triangle = {
    corners: {},
    angles:{},
    sides: {},
    create: function (a,b,c,d,e,f) {
        this.corners.A = [ a, b ],
        this.corners.B = [ c, d ],
        this.corners.C = [ e, f ]
        return this;
    },
    distance: function (q,w) {
        let x = q[0] - w[0],
            y = q[1] - w[1];

        return Math.sqrt(  Math.pow(x,2) +     Math.pow(y,2))
    },
    largest_side: function() {
      let largest_length = Math.max(this.sides.a, this.sides.b, this.sides.c);
      let largest_side = Object.keys(this.sides).filter ( key => {
        return this.sides[key] == largest_length;
      });
      return largest_side[0];
    },
    find_angle: function (a,b,c) {
      return Math.acos( (Math.pow(a,2) + Math.pow(c,2) -Math.pow(b,2) ) / (2 * a  * c)) * ( 180 / Math.PI )
    },
    lengths: function () {
        this.sides.a = this.distance(this.corners.C,this.corners.B);
        this.sides.b = this.distance(this.corners.A,this.corners.C);
        this.sides.c = this.distance(this.corners.A,this.corners.B);
        return this;
    },
    calc_angles:function(){
      // largets angle first
        let l_side = this.largest_side();
        let other_sides = ['a','b', 'c'].filter( side => {
           return side != l_side;
        });
        let adj1 = this.sides[other_sides[0]];
        let adj2 = this.sides[other_sides[1]];
        this.angles[l_side] = this.find_angle(adj1, this.sides[l_side], adj2);
        // calculate remaining angles
        
        return this;
    }
}
console.log(triangle.create(-2,-2,3,-1,1,3).lengths().calc_angles());