51help TIY
码：
<html> <body> <script type="text/javascript"> document.write(Math.acos(0.64) + "<br />") document.write(Math.acos(0) + "<br />") document.write(Math.acos(-1) + "<br />") document.write(Math.acos(1) + "<br />") document.write(Math.acos(2)) </script> </body> </html>
查看结果: