circle trigonometry

Question

Identify the point (x,y) on the unit circle the corresponds to t= -13pi/6

Answer 1

Coterminal angle t' = -13π/6 + 2π = - π/6

x = cos(-π/6) = √3/2; y = sin(-π/6) = - 1/2

(x,y) = (√3/2, - 1/2)

Answer 2

(x, y) = (cos(-13π/6), sin(-13π/6)) = (cos(-π/6), sin(-π/6)) = (cos(π/6), -sin(π/6)) = (√3/2, -1/2)