I have to find the coordinates for S(i).

My attempt :

OP = 1 * 1/2 = 1/2

(1/2)^{2}+ x^{2 }= 1^{2}

x = √(3)/2

cos^{-1}(√(3)/2) = 30

sin^{-1}(1/2) = 30

t = 30

cos(2*t) = cos(60) = 1/2

sin(2*t) = sin(60) =√(3)/2

S(i) = (1,2 , √(3)/2 )