Question

    If cos θ + sec θ = √2, then the value of cos³ θ+

    sec³ θ is:
    A √2 Correct Answer Incorrect Answer
    B 1/√2 Correct Answer Incorrect Answer
    C -√2 Correct Answer Incorrect Answer

    Solution

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

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