SIN(X) returns the sine of X, where X is given in radians : SIN « Math Numeric Functions « MySQL Tutorial

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

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

mysql>
mysql> SELECT ROUND(SIN(PI()));
+------------------+
| ROUND(SIN(PI())) |
+------------------+
|                0 |
+------------------+
1 row in set (0.00 sec)

mysql>