If tan ( (π)/2 - 3θ) = 1/(√3) , the value of cos3θ is?

tan (\(\frac{π}{2}\) - 3θ) = \(\frac{1}{√3}\)

⇒ tan (\(\frac{π}{2}\) - 3θ) = tan 30°

⇒ 90 - 3θ = 30°

⇒ 3θ = 60° ⇒  θ = 20°

cos 3θ = cos 60° = \(\frac{1}{2}\)