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    Question

    If 4cos²A + 5sin²A = 4.5, then find the value of (sec²A

    - 1)
    A 1/2 Correct Answer Incorrect Answer
    B 1 Correct Answer Incorrect Answer
    C 3/2 Correct Answer Incorrect Answer
    D 2/3 Correct Answer Incorrect Answer

    Solution

    4cos²A + 5sin²A = 4.5
    Or, -1cos²A + 5(cos²A + sin²A) = 4.5
    Or, -cos²A + 5 = 4.5 (Using cos²A + sin²A = 1)
    Or, -cos²A = -0.5 => cos²A = 0.5
    So, sec²A = 1/0.5 = 2
    Required value = 2 - 1 = 1

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