A company uses a simplified model where customer preference vectors lie on the unit circle. Whether the vector (0.8, 0.6) lies on the unit circle?

No — because both coordinates are less than 1.

Yes — x^2 + y^2 = 1 so it lies on the unit circle.

No — because the x-coordinate is not an exact rational square root fraction like 1/2 or √3/2

Yes — but only after scaling by the factor of 1.25