TAN(X) returns the tangent of X, where X is given in radians. : TAN « Math Numeric Functions « MySQL Tutorial

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

mysql>
mysql> SELECT TAN(PI());
+-----------------------+
| TAN(PI())             |
+-----------------------+
| -1.2246063538224e-016 |
+-----------------------+
1 row in set (0.00 sec)

mysql>
mysql> SELECT TAN(PI()+1);
+-----------------+
| TAN(PI()+1)     |
+-----------------+
| 1.5574077246549 |
+-----------------+
1 row in set (0.00 sec)