JEE Main & Advanced Sample Paper JEE Main Sample Paper-39

  • question_answer
    The x satisfying\[{{\sin }^{-1}}x+{{\sin }^{-1}}(1-x)={{\cos }^{-1}}x\]are

    A)  1, 0                            

    B)  1,-1

    C)  \[0,\frac{1}{2}\]                    

    D)  None of these

    Correct Answer: C

    Solution :

     \[{{\sin }^{-1}}(1-x)=\left( \frac{\pi }{2}-{{\sin }^{-1}}x \right)-{{\sin }^{-1}}x\] \[(\because {{\cos }^{-1}}x=\frac{\pi }{2}-{{\sin }^{-1}}x)\] \[{{\sin }^{-1}}(1-x)=\frac{\pi }{2}-2{{\sin }^{-1}}x\] Taking sum of both sides \[1-x=\sin \left( \frac{\pi }{2}-2{{\sin }^{-1}}x \right)=(2{{\sin }^{-1}}x)\] \[=\cos 2\theta ,\]where \[{{\sin }^{-1}}x=\theta \] \[1-x=1-2{{\sin }^{2}}\theta =1-2{{x}^{2}}\]or \[x(1-2x)=0\]or \[x=0,\frac{1}{2}\]


You need to login to perform this action.
You will be redirected in 3 sec spinner