ATAN(X) returns the arc tangent of X : ATAN « Math Numeric Functions « MySQL Tutorial

1. MySQL Tutorial
2. Math Numeric Functions
3. ATAN

mysql>
mysql> SELECT ATAN(2);
+-----------------+
| ATAN(2)         |
+-----------------+
| 1.1071487177941 |
+-----------------+
1 row in set (0.02 sec)

mysql> SELECT ATAN(-2);
+------------------+
| ATAN(-2)         |
+------------------+
| -1.1071487177941 |
+------------------+
1 row in set (0.00 sec)

mysql>