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    Question

    If cos θ + sec θ = √5, then the value of cos³ θ+

    sec³ θ is:
    B 2√5 Correct Answer Incorrect Answer
    C 1/√5 Correct Answer Incorrect Answer
    D √5 Correct Answer Incorrect Answer

    Solution

    cos θ + sec θ = √5 cos³ θ+ sec³ θ = (cos θ + sec θ)3 - 3 ×cos θ × sec θ (cos θ + sec θ) = (√5)3 - 3× cos θ×1/ cos θ (√5) =5√5 -3√5 =2√5

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