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

    Question

    If 2cosec 2  A – cot 2  A = 5 and

    0 o  < A < 90 o , then find the value of ‘A’.
    A 30° Correct Answer Incorrect Answer
    B 60° Correct Answer Incorrect Answer
    C 120° Correct Answer Incorrect Answer
    D 150° Correct Answer Incorrect Answer

    Solution

    2cosec² A – cot² A = 5
    Using, cosec² A = 1 + cot² A
    We have, 2cosec² A – (cosec² A – 1) = 5
    Or, 2cosec² A – cosec² A + 1 = 5
    Or, cosec² A = 4
    Or, cosec A = 2 or – 2
    So, ‘A’ = 30° and 150°
    Since, 0° < A < 90°, so ‘A’ = 30°

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