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    Question

    If cos2B = sin(1.5B - 36 o ) , then find the

    measure of 'B'.
    A 14° Correct Answer Incorrect Answer
    B 36° Correct Answer Incorrect Answer
    C 30° Correct Answer Incorrect Answer
    D 26° Correct Answer Incorrect Answer

    Solution

    We know that, cosA = sin(90 o  - A)

    cos2B = sin(1.5B - 36 o )

    Or, sin(90 o  - 2B) = sin(1.5B - 36 o )

    Or, 90 o  - 2B = 1.5B - 36 o

    Or, 2B + 1.5B = 90 o  + 36 o

    So, B = (126 o /3.5) = 36 o

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