acosh(float X);
<?Php echo acosh(6); // Output 2.4778887302885 echo "<br>"; echo acosh(2.5); // Output 1.5667992369724 echo "<br>"; echo acosh(0); // Output NAN echo "<br>"; echo acosh(2); // Output 1.3169578969248 echo "<br>"; echo acosh(-2.5); // Output NAN echo "<br>"; echo acosh(-4); // Output NAN ?>
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