JEE Main & Advanced Mathematics Inverse Trigonometric Functions Question Bank Self Evaluation Test - Inverse Trigonometric Functions

  • question_answer
    Total number of positive integral value ?n? so that the equations \[{{\cos }^{-1}}x+{{(si{{n}^{-1}}y)}^{2}}=\frac{n{{\pi }^{2}}}{4}\] and \[{{(si{{n}^{-1}}y)}^{2}}-{{\cos }^{-1}}x=\frac{{{\pi }^{2}}}{16}\] are consistent, is equal to

    A) 1

    B) 4

    C) 3

    D) 2

    Correct Answer: A

    Solution :

    [a] We have, \[2{{(si{{n}^{-1}}y)}^{2}}=\frac{4n+1}{16}{{\pi }^{2}}\] \[\Rightarrow 0\le \frac{4n+1}{32}{{\pi }^{2}}\le \frac{{{\pi }^{2}}}{4}\] Also, \[2(co{{s}^{-1}}x)=\frac{4n-1}{16}{{\pi }^{2}}\Rightarrow -\frac{1}{4}\le n\le \frac{7}{4}\] Also, \[2(co{{s}^{-1}}x)=\frac{4n-1}{16}{{\pi }^{2}}\] \[\Rightarrow 0\le \frac{4n-1}{32}{{\pi }^{2}}\le \pi \Rightarrow \frac{1}{4}\le n\,\le \frac{8}{\pi }+\frac{1}{4}\Rightarrow n=1\]


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