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<!DOCTYPE html>
<html>
<body>
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<h1>JavaScript Math.sin()</h1>
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<p>Math.sin(x) 返回 x（以弧度计）的正弦：</p>
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<p>以弧度计的角度 = (以度数计的角度) * PI / 180。</p>
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<p id="demo"></p>
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<script>
document.getElementById("demo").innerHTML = 
"The sine value of 90 degrees is " + Math.sin(90 * Math.PI / 180);
</script>
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</body>
</html>
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