JavaScript canvas Math 报错帮忙看看感谢!

 <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>3-2 画一个五角星</title>
</head>
<body>

<canvas id="canvas" style="border: 1px solid #aaa; display: block;margin: 50px auto;">当前浏览器不支持Canvas,请更换浏览器再试</canvas>

<script>
    window.onload = function(){
        var canvas = document.getElementById("canvas");

        canvas.width = 800;
        canvas.height = 800;

        var context = canvas.getContext("2d"); //context绘制




        context.lineWidth = 10;
        drawStar(context, 150, 300, 400, 400);
    }

    function drawStar(cxt, r, R, x, y){

        cxt.beginPath();
        for (var i = 0; i < 5; i ++){
            cxt.lineTo( Math.cos( (18 + i * 72) / 180 * Math.PI ) * R + x,
                -Math.sin( 18 + i * 72) / 180 * Math.PI ) * R + y);
            cxt.lineTo( Math.cos( (54 + i * 72) / 180 * Math.PI ) * r + x,
                -Math.sin(54 + i * 72) / 180 * Math.PI ) * r + y);
    }
    cxt.closePath();
    cxt.stroke();
    }


</script>

</body>
</html>

 少括号了吧
 -Math.sin( 18 + i * 72) / 180 * Math.PI ) * R + y)
 -Math.sin(54 + i * 72) / 180 * Math.PI ) * r + y);
 改成,加一个(
 -Math.sin(( 18 + i * 72) / 180 * Math.PI ) * R + y)
 -Math.sin((54 + i * 72) / 180 * Math.PI ) * r + y);

你好我试了一下还是有问题

你的绘制图形的句子不标准，for循环内出错，应该是先moveTo，后面的先lineTo

JavaScript canvas Math 报错 帮忙看看 感谢!

JavaScript canvas Math 报错帮忙看看感谢!