Question

Which of the following could not be points on the unit circle?

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Answer 1

A, C

Explanation:

For a point to be on the unit circle, it must be a solution to ...

x² +y² = 1

__

The sums of squares of the x- and y-values are ...

A: 1² +1² = 2 . . . not on the circle

B: (-2/3)² +(√5/3)² = (4+5)/9 = 1

C: (√3/2)² +(-1/3)² = 3/4 +1/9 = 31/36 . . . not on the circle

D: 0.8² +(-0.6)² = .64 +.36 = 1

Points A and C do not lie on a unit circle.