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    Question

    If cosB = sin(1.5B - 15°), then find the measure of

    'B'.
    A 42° Correct Answer Incorrect Answer
    B 30° Correct Answer Incorrect Answer
    C 36° Correct Answer Incorrect Answer
    D 26° Correct Answer Incorrect Answer

    Solution

    We know that, cosA = sin(90° - A) cosB = sin(1.5B - 15°) Or, sin(90° - B) = sin(1.5B - 15°) Or, 90° - B = 1.5B - 15° Or, B + 1.5B = 90° + 15° So, B = (105° / 2.5) = 42°

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