Find the value of cos(2pi/3

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

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