Question

cos 3 theta = cos (theta - 20 degree) .... Value of theta?

Answer 1

Answer :

Now,

cos3θ = cos (θ - 20°)

or, 3θ = θ - 20°

or, 3θ - θ = - 20°

or, 2θ = - 20°

or, θ = - 20°/2

or, θ = - 10°

Therefore, the value of θ is (- 10°)

Also,

cos3θ = cos (θ - 20)

or, cos3θ = cos (20° - θ)

or, 3θ = 20° - θ

or, 3θ + θ = 20°

or, 4θ = 20°

or, θ = 5°

Therefore, the value of θ is 5°

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