MySQL ACOS() 反余弦函数
ACOS(x)
函数返回x的反余弦值;如果x不在定义域[-1,1]
中,将返回NULL
;
SELECT ACOS(-1);
+-------------------+
| ACOS(-1) |
+-------------------+
| 3.141592653589793 |
+-------------------+
1 row in set (0.00 sec)
SELECT ACOS(1.1);
+-----------+
| ACOS(1.1) |
+-----------+
| NULL |
+-----------+
1 row in set (0.00 sec)