JEE Main & Advanced Mathematics Trigonometric Identities Question Bank Fundamental trigonometrical ratios and functions, Trigonometrical ratio of allied angles

  • question_answer
    If \[\tan A+\cot A=4,\]then \[{{\tan }^{4}}A+{{\cot }^{4}}A\] is equal to   [Kerala (Engg.) 2002]

    A) 110

    B) 191

    C) 80

    D) 194

    Correct Answer: D

    Solution :

    \[\tan A+\cot A=4\] \[\Rightarrow \,{{\tan }^{2}}A+{{\cot }^{2}}A+2\,\tan A\,\,\cot A=16\] \[\Rightarrow \,{{\tan }^{2}}A+{{\cot }^{2}}A=14\,\,\Rightarrow \,{{\tan }^{4}}A+{{\cot }^{4}}A+2=196\] \[\Rightarrow \,{{\tan }^{4}}A+{{\cot }^{4}}A=194.\]


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