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    ​If tan (3A) = cot (A - 22°), where 3A is an acute angle, then what is the value of A?​
    Question

    If tan (3A) = cot (A - 22°), where 3A is an acute angle, then what is the value of A?

    A.

    25°

    B.

    27°

    C.

    28°

    D.

    30°

    Correct option is C

    Given:

    tan(3A) = cot(A - 22°), where 3A is an acute angle,

    Solution:

    cot(x) = tan(90° - x).

    tan(3A) = tan(90°−(A−22°))

    tan(3A) = tan(90°−A+22°)

    tan(3A) = tan(112°−A)

    Since the tangent function is periodic with a period of 180°, we have:

    3A=112°−A+n180°

    where is an integer. Since 3A is an acute angle, (i.e. (0  < A < 90).

    3A = 112- A

    4A = 112

    A = 28

    ∴ The correct answer is 28.

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