To find the x-value (or cosine value) at 150°, we can use the unit circle.
At 150°, the coordinates of the point on the unit circle can be found as follows:
The angle 150° is in the second quadrant, and we can determine its reference angle:
\[ 150° - 90° = 60° \]
In the second quadrant, the cosine value (which gives the x-coordinate) is negative, while the sine value (y-coordinate) is positive. The cosine of 60° is \( \frac{1}{2} \). Therefore, the cosine of 150° would be:
\[ \cos(150°) = -\cos(60°) = -\frac{1}{2} \]
Thus, the x-value at 150° is:
\[ -\frac{1}{2} \]