SQL/MySQL/Math/ATAN

Use and ATAN and ATAN2

/*
mysql> select ATAN(1, 2);
+------------------+
| ATAN(1, 2)       |
+------------------+
| 0.46364760900081 |
+------------------+
1 row in set (0.00 sec)
mysql> select ATAN2(1, 2);
+------------------+
| ATAN2(1, 2)      |
+------------------+
| 0.46364760900081 |
+------------------+
1 row in set (0.00 sec)

*/  
select ATAN(1, 2);
select ATAN2(1, 2);

Use ATAN

/*
mysql> select ATAN( 0.45);
+------------------+
| ATAN( 0.45)      |
+------------------+
| 0.42285392613294 |
+------------------+
1 row in set (0.00 sec)

*/  
select ATAN( 0.45);