New RBI Grade B 2025 Notification will come Soon! Enroll Here

    Question

    If tan 4θ = cot 14θ, then find the value of cos

    9θ.
    A (√3/2) Correct Answer Incorrect Answer
    B (1/√2) Correct Answer Incorrect Answer
    D 1 Correct Answer Incorrect Answer

    Solution

    tan 4θ = cot 14θ Or, tan 4θ = cot (90o - 4θ) [because, tan A = cot (90o - A) ] Or, 14θ = 90o - 4θ Or, 18θ = 90o Or, θ = (90/18) o = 5o So, cos 9θ = cos 45o = (1/√2)

    Practice Next