
    context.stroke();
    context.closePath();
}

// polynomial
var polynomial_xs = [2.0, 4.0, 6.0];
var polynomial_ys = [4.0, 2.0, 4.0];
var polynomial_n = 3;
var polynomial_i = 0;

function points_ok() {
    if(polynomial_xs[0].toFixed(1) == polynomial_xs[1].toFixed(1)
      || polynomial_xs[1].toFixed(1) == polynomial_xs[2].toFixed(1)
      || polynomial_xs[2].toFixed(1) == polynomial_xs[0].toFixed(1))
       return false;
    return true;
}

function init_polynomial(){
    polynomial = document.getElem