JEE Main & Advanced Sample Paper JEE Main Sample Paper-47

  • question_answer
    Direction: We have,
    \[x<0\] \[x\ge 0\]
    \[\frac{-\pi }{2}\le {{\sin }^{-1}}x<0\] \[0\le \,{{\sin }^{-1}}x\le \frac{\pi }{2}\]
    \[\frac{\pi }{2}<{{\cos }^{-1}}x\le \pi \] \[0\le {{\cos }^{-1}}x\le \frac{\pi }{2}\]
    Then,
    The principal value of \[{{\sin }^{-1}}(\sin 5)-{{\cos }^{-1}}(\cos 5)\] is

    A)  0                                

    B)  \[2\pi -10\]

    C)  \[-\pi \]                       

    D)  \[3\pi -10\]

    Correct Answer: C

    Solution :

     \[\because \]    \[5=5\times {{57}^{o}}\approx {{285}^{o}}\] \[\therefore \]    \[\sin \,5<0\] and \[\cos \,5\,<0\] \[\Rightarrow \] \[{{\sin }^{-1}}\,(\sin \,5)\,={{\sin }^{-1}}\,\{\sin \,(\pi -5)\}\,=\pi -5\] and \[{{\cos }^{-1}}\,(\cos \,5)=co{{s}^{-1}}\,\{\cos \,(2\pi -5)\}\] \[=2\pi -5\] \[\therefore \]    \[{{\sin }^{-1}}(\sin \,5)\,-{{\cos }^{-1}}\,(\cos \,5)\] \[=\pi -5-2\pi +5=-\pi \]


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