tryphp_func_math_acos.php:
"); echo(acos(-0.4) . "
"); echo(acos(0) . "
"); echo(acos(-1) . "
"); echo(acos(1) . "
"); echo(acos(2)); ?>
0.87629806116834
1.9823131728624
1.5707963267949
3.1415926535898
0
NAN