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    Question

    If cos2B = sin(1.5B + 48o), then find the

    measure of 'B'.
    A 8° Correct Answer Incorrect Answer
    B 12° Correct Answer Incorrect Answer
    C 16° Correct Answer Incorrect Answer
    D 20° Correct Answer Incorrect Answer

    Solution

    We know that, cosA = sin(90 o - A) cos2B = sin(1.5B + 48 o) Or, sin(90 o - 2B) = sin(1.5B + 48 o) Or, 90 o - 2B = 1.5B + 48 o Or, 2B + 1.5B = 90 o - 48 o So, 3.5B = 42 o So, B = (42o/ 3.5) = 12o Hence, option b.

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