School geometry

geometry.js

/* Get equation of line going through 2 points */
function getLine(point0, point1) {
    var k = (point1[1] - point0[1]) / (point1[0] - point0[0]);
    var b =  -k * point0[0] + point0[1];

    return {
        k: k,
        b: b,
        y: function (x) { return k * x + b; }
    };
}

/* Get equation of perpendicular line crossing in point */
function getPerpendicular(point, line) {
    var k = -1 / line.k;

    return {
        y: function (x) {
            return (x - point[0]) * k + point[1];
        },
        x: function (y) {
            return (y - point[1]) / k + point[0];
        }
    };
}