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<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <title>五角星</title> <script> window.onload = function () { var canvas = document.getElementById("canvas"); if (canvas) { var context = canvas.getContext("2d"); drawStar(context, 50, 100, 100); } } function drawStar(context, r, x, y) { context.lineWidth = 5; context.beginPath(); var dit = Math.PI * 4 / 5; var sin = Math.sin(0) * r + y; var cos = Math.cos(0) * r + x; console.log(0+":"+0); context.moveTo(cos, sin); for (var i = 0; i < 5; i++) { var tempDit = dit * i; sin = Math.sin(tempDit) * r + y; cos = Math.cos(tempDit) * r + x; context.lineTo(cos, sin); console.log(sin+":"+sin+":"+tempDit); } context.closePath(); context.strokeStyle = "red"; context.fillStyle = "#DDDDDD"; context.fill(); } </script> </head> <body> <canvas id="canvas"></canvas> </body> </html>
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