Final answer:
The cosine of 270 degrees is 0, as the point on the unit circle at this angle has an x-coordinate of 0.
Step-by-step explanation:
The cos(270 degrees) refers to the cosine function evaluated at an angle of 270 degrees. In the unit circle, which is commonly used in trigonometry to define the sine and cosine of an angle, the point at 270 degrees is directly below the center at the coordinates (0, -1). Therefore, the cosine of 270 degrees, which corresponds to the x-coordinate in the unit circle, is 0.