what point on the unit circle corresponds to

Question

what point on the unit circle corresponds to -2π/3

 

A.(-√3/2,-1/2)

B.(-√2/2,-√2/2)

C.(-1/2,-√3/2)

D.(-1,0)

 

Answer 1

First of all, the point corresponding to an angle θ on the unit circle has the coordinates (cos θ, sin θ).

 

Second, to make it a little easier, -2π/3 is coterminal with 4π/3, since 2π + (-2π/3) = 4π/3.

 

cos (4π/3) = -1/2

sin (4π/3) = -√3 / 2

 

So the answer is C