JSFiddle - React, Tailwind, and code Playground

HTML

<title>Title of the document</title>
<script>
function My(canvas, opts){
    this.canvas = canvas;
    this.ctx = canvas.getContext('2d');
    this.opts = opts || {};
    this.opts.pSize = this.opts.pSize || 3;
}
My.prototype.P = function(x,y,color){
    var ctx = this.ctx;
    var a = this.opts.pSize;
    ctx.strokeStyle = color||'black';
    ctx.beginPath();
    ctx.moveTo(x-a,y-a);
    ctx.lineTo(x+a, y+a);
    ctx.closePath();
    ctx.stroke();
    ctx.beginPath();
    ctx.moveTo(x-a, y+a);
    ctx.lineTo(x+a, y-a);
    ctx.closePath();
    ctx.stroke();
}

My.prototype.L = function(x,y,x2,y2,color){
    var ctx = this.ctx;
    ctx.strokeStyle = color||'black';
    ctx.beginPath();
    ctx.moveTo(x,y);
    ctx.lineTo(x2,y2);
    ctx.closePath();
    ctx.stroke();
}
My.prototype.C = function(x,y,R,color){
    var ctx = this.ctx;
    ctx.strokeStyle = color||'black';
    ctx.beginPath();
    ctx.arc(x,y,R,0,2*Math.PI);
    ctx.closePath();
    ctx.stroke();
}
My.prototype.clear = function(){
    var ctx = this.ctx;
    ctx.save();
    ctx.setTransform(1,0,0,1,0,0);
    ctx.clearRect(0,0,this.canvas.width,this.canvas.height);
    ctx.restore();
}
</script>

<body>
<canvas width=800 height=800></canvas>
<form method="" action="#">
R <input type="text" value="200" name="R"/><br/>
L <input type="text" value="400" name="L"/><br/>
C <input type="text" value="150" name="C"/><br/>
<input type="submit" value="refresh"/>
</form>
<script>
function solve(R,L,C){
    //http://stackoverflow.com/questions/27176423/function-to-solve-cubic-equation-analytically
    function cuberoot(x) {
        var y = Math.pow(Math.abs(x), 1/3);
        return x < 0 ? -y : y;
    }

    function solveCubic(a, b, c, d) {
        if (Math.abs(a) < 1e-8) { // Quadratic case, ax^2+bx+c=0
            a = b; b = c; c = d;
            if (Math.abs(a) < 1e-8) { // Linear case, ax+b=0
                a = b; b = c;
                if (Math.abs(a) < 1e-8) // Degenerate case
                    return...

CSS

canvas{
    background:#eeeeee;
}