<?PHP echo asin ( 1.0 ); echo '<br>'; echo asin ( 0.52 ); echo '<br>'; echo asin ( -1.00 ); echo '<br>'; echo asin ( -1.01 ); echo '<br>'; echo rad2deg ( asin ( 0.50 ) ) . '°'; ?>
1.5707963267949 0.54685095069594 -1.5707963267949 NAN 30°