To find the y-value at \( 330^\circ \), we can use the unit circle.
The angle \( 330^\circ \) is in the fourth quadrant, where the sine function (which corresponds to the y-coordinate) is negative.
The reference angle for \( 330^\circ \) is: \[ 360^\circ - 330^\circ = 30^\circ \]
The sine of \( 30^\circ \) is: \[ \sin(30^\circ) = \frac{1}{2} \]
Since \( 330^\circ \) is in the fourth quadrant, the y-value is negative: \[ \sin(330^\circ) = -\sin(30^\circ) = -\frac{1}{2} \]
Therefore, the y-value at \( 330^\circ \) is: \[ \boxed{-\frac{1}{2}} \]