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    Question

    Simplify the following trigonometric expression: 12

    cos 68o cosec 22o - 3 cot 72o cot 18o
    A 1 Correct Answer Incorrect Answer
    C 15 Correct Answer Incorrect Answer
    D 9 Correct Answer Incorrect Answer

    Solution

    12cos 68o cosec 22o - 3cot 72o cot 18o

    = 12cos 68o cosec (90o - 68o) - 3cot 72o cot (90o - 72o)

    Using, cosec (90o - A) = sec A and cot (90o - A) = tan A

    = 12 cos 68o sec 68o - 3 cot 72o tan 72o

    Since, sec A is reciprocal of cos A and cot A is reciprocal of tan A.

    = 12 - 3 = 9

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