New Enroll in RBI Grade B New Batch - Starts on May 21

    Question

    If (sin 3A sec 6A = 1) , then what will be the value of cos

    6A?
    A 1/2 Correct Answer Incorrect Answer
    B √3/2 Correct Answer Incorrect Answer
    D 1 Correct Answer Incorrect Answer

    Solution

    sin 3A sec 6A = 1

    Or, sin 3A = (1/sec 6A)

    We know that, sec P is the reciprocal of cos P

    Or, sin 3A = cos 6A

    We know that, cos P = sin (90 - P)

    Or, sin 3A = sin (90 - 6A)

    Or, 3A = 90 - 6A

    Or, 9A = 90

    So, 'A' = 10

    Required value = cos 6A = cos 60 o  = (1/2)

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