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<h2 id="number">87.6899487</h2>
<h2>你是數字嗎:<span id="isNaN"></span></h2>
<h2>四捨五入到小數點後第二位:<span id="toFixed"></span></h2>
<h2>四捨五入(從整數第一位開始數):<span id="toPrecision"></span></h2>
<h2>以指數方式顯示:<span id="toExponential"></span></h2>
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