Final answer:
The exact value of cosine 270 degrees on the unit circle is 0.
Step-by-step explanation:
To find the exact value of cosine 270 degrees, we look at the unit circle where the angle 270 degrees corresponds to the point on the circle located at π/2 radians or 3π/2 radians. At this position, the x-coordinate (which represents the cosine value) is 0, and the y-coordinate (representing the sine value) is -1. However, since we are only looking for the cosine, the exact value of cosine 270 degrees is 0. The cosine of an angle is the x-coordinate of the point where the terminal side of the angle intersects the unit circle. For 270 degrees, the terminal side lies on the negative y-axis, so the x-coordinate is 0.