Of the four x-coordinates to choose only 1/√(11) belongs can belong to the unit circle.
The other three x-coordinates are greater than 1, then they are out of the unit circle.
The unit circle formula is x^2 +y^2 = 1
Then to find the y-coordinate given the x-coordinate you can solve for y from that formula:
y^2 = 1 - x^2
y = (+/-)√(1-x^2)
Substitute the value of x
y = (+/-)√{1 - [1/√(11)]^2} = (+/-) √{(1 - 1/11} =(+/-) √ {(11 -1)/11 =(+/-)√(10/11) ≈ +/- 0.95
