my flash triangle

public function IsIn(v : vector2) : Boolean
        {
            var xaxis1 : vector2 = new vector2(v2.x - v1.x, v2.y - v1.y);
            var yaxis1 : vector2 = new vector2(v3.x - v1.x, v3.y - v1.y);

            var a11 = xaxis1.x;
            var a12 = xaxis1.y;
            var a21 = yaxis1.x;
            var a22 = yaxis1.y;

            var det : Number = (a11 * a22 - a21 * a12);
            var fa11 : Number = a22 / det;//(a11 * a22 - a21 * a12);
            var fa12 : Number = -a12 / det;// (yaxis1.y * xaxis1.x - xaxis1.y * yaxis1.x);
            var fa21 : Number = -a21 / det;//(yaxis1.y * xaxis1.x - xaxis1.y * yaxis1.x);
            var fa22 : Number = a11 / det;//(yaxis1.y * xaxis1.x - xaxis1.y * yaxis1.x);

            var nv:vector2 = new vector2(0, 0);
            nv.x = v.x - v1.x;
            nv.y = v.y - v1.y;
            var vc : vector2 = new vector2(nv.x * fa11 + nv.y * fa21, nv.x * fa12 + nv.y * fa22);
            if (vc.x > 0 && vc.y > 0 && ((vc.x < (1.0-vc.y))) && vc.x <= 1.0 && vc.y <=1.0)
            {
                trace("in");
                return true;
            }
            return false;
        }