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    Question

    If 9sin²x + 5cos²x − 7 = 0, then find the value of

    sinx, given that 0° < x < 90°.
    A 1 Correct Answer Incorrect Answer
    B 1/√2 Correct Answer Incorrect Answer
    C 1/2 Correct Answer Incorrect Answer
    D √3/2 Correct Answer Incorrect Answer

    Solution

    Given
    9sin²x + 5cos²x = 7 Or,
    9sin²x + 5(1 − sin²x) = 7 Or,
    9sin²x + 5 − 5sin²x = 7 Or,
    4sin²x = 2 Or,
    sin²x = (1/2) Or,
    sinx = (1/√2) (since, 0° < x < 90°)

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