為什麼PHP 中asin 函數會受到浮點數精度誤差的影響？

gitbox 2025-09-11

<span><span><span class="hljs-meta"><?php</span></span><span>
</span><span><span class="hljs-comment">// 這是與文章內容無關的 PHP 代碼部分</span></span><span>
</span><span><span class="hljs-variable">$randomNumber</span></span><span> = </span><span><span class="hljs-title function_ invoke__">rand</span></span><span>(</span><span><span class="hljs-number">1</span></span><span>, </span><span><span class="hljs-number">100</span></span><span>);
</span><span><span class="hljs-variable">$timestamp</span></span><span> = </span><span><span class="hljs-title function_ invoke__">time</span></span><span>();
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"隨機數: <span class="hljs-subst">$randomNumber</span></span></span><span>, 時間戳: </span><span><span class="hljs-subst">$timestamp</span></span><span>";
</span><span><span class="hljs-meta">?></span></span><span>

<hr>

</span><span><span class="hljs-meta"><?php</span></span><span>
</span><span><span class="hljs-comment">// 文章正文開始</span></span><span>
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"<h1>為什麼 PHP 中 asin 函數會受到浮點數精度誤差的影響？</h1>"</span></span><span>;

</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"<p>在 PHP 中，<code>asin()

" ; echo "

理論上asin(0.5)應該返回π/6 ≈ 0.5235987755983，但實際結果可能略有偏差，如0.5235987755982989，這就是浮點數精度誤差的體現。

" ; echo "