# Simplify trigonometric expression

How can I do to obtain 0 in place of:

```
-1/2*sin(1/16*pi)*sin(3/16*pi)*sin(5/16*pi)*sin(7/16*pi) -
1/2*sin(1/8*pi)*sin(3/8*pi)*sin(5/8*pi)*sin(7/8*pi) -
1/2*sin(3/16*pi)*sin(9/16*pi)*sin(15/16*pi)*sin(21/16*pi) -
1/2*sin(5/16*pi)*sin(15/16*pi)*sin(25/16*pi)*sin(35/16*pi) -
1/2*sin(3/8*pi)*sin(9/8*pi)*sin(15/8*pi)*sin(21/8*pi) -
1/2*sin(7/16*pi)*sin(21/16*pi)*sin(35/16*pi)*sin(49/16*pi) -
1/2*sin(9/16*pi)*sin(27/16*pi)*sin(45/16*pi)*sin(63/16*pi) -
1/2*sin(5/8*pi)*sin(15/8*pi)*sin(25/8*pi)*sin(35/8*pi) -
1/2*sin(11/16*pi)*sin(33/16*pi)*sin(55/16*pi)*sin(77/16*pi) -
1/2*sin(13/16*pi)*sin(39/16*pi)*sin(65/16*pi)*sin(91/16*pi) -
1/2*sin(7/8*pi)*sin(21/8*pi)*sin(35/8*pi)*sin(49/8*pi) -
1/2*sin(15/16*pi)*sin(45/16*pi)*sin(75/16*pi)*sin(105/16*pi) +
1/2*cos(1/16*pi)*cos(3/16*pi)*cos(5/16*pi)*cos(7/16*pi) +
1/2*cos(1/8*pi)*cos(3/8*pi)*cos(5/8*pi)*cos(7/8*pi) +
1/2*cos(3/16*pi)*cos(9/16*pi)*cos(15/16*pi)*cos(21/16*pi) +
1/2*cos(5/16*pi)*cos(15/16*pi)*cos(25/16*pi)*cos(35/16*pi) +
1/2*cos(3/8*pi)*cos(9/8*pi)*cos(15/8*pi)*cos(21/8*pi) +
1/2*cos(7/16*pi)*cos(21/16*pi)*cos(35/16*pi)*cos(49/16*pi) +
1/2*cos(9/16*pi)*cos(27/16*pi)*cos(45/16*pi)*cos(63/16*pi) +
1/2*cos(5/8*pi)*cos(15/8*pi)*cos(25/8*pi)*cos(35/8*pi) +
1/2*cos(11/16*pi)*cos(33/16*pi)*cos(55/16*pi)*cos(77/16*pi) +
1/2*cos(13/16*pi)*cos(39/16*pi)*cos(65/16*pi)*cos(91/16*pi) +
1/2*cos(7/8*pi)*cos(21/8*pi)*cos(35/8*pi)*cos(49/8*pi) +
1/2*cos(15/16*pi)*cos(45/16*pi)*cos(75/16*pi)*cos(105/16*pi)
```