Question

If cosθ = 0.2, find the value of cosθ + cos (θ + 2π) + cos (θ + 4π)

Answer 1

We know that cos(θ + 2π) = cosθ and cos(θ + 4π) = cosθ.

Therefore,

cosθ + cos(θ + 2π) + cos(θ + 4π)
= cosθ + cosθ + cosθ
= 3cosθ

Substituting cosθ = 0.2, we get:

cosθ + cos(θ + 2π) + cos(θ + 4π) = 3cosθ = 3(0.2) = 0.6

Therefore, cosθ + cos(θ + 2π) + cos(θ + 4π) = 0.6.