We have to find the value of cos(2π/3)
Solution
π= 180
cos(2π/3) = 360/3
cos(2π/3) = 120
120° can be represented in terms of two angles i.e. either 90° or 180°
Cos 120° = cos(180° – 60°) = – cos 60° = -½ (since cos(180° – x) = – cos x)
Cos 120° = cos(90° + 30°) = – sin 30° = -½ (we know that cos (90° + x) = -sin x)
Answer
cos(2π/3)= -1/2
