mysql>
mysql>
mysql> SELECT ATAN(-2,2);
+-------------------+
| ATAN(-2,2) |
+-------------------+
| -0.78539816339745 |
+-------------------+
1 row in set (0.00 sec)
mysql> SELECT ATAN2(PI(),0);
+-----------------+
| ATAN2(PI(),0) |
+-----------------+
| 1.5707963267949 |
+-----------------+
1 row in set (0.00 sec)
mysql>