KVPY Sample Paper KVPY Stream-SX Model Paper-23

  • question_answer
    Number of ordered pairs \[(a,x)\] satisfying the equation \[{{\sec }^{2}}\,(a+2)x+{{a}^{2}}-1=0;-\pi <x<\pi \] is

    A) 1

    B) 2      

    C) 3

    D) 4

    Correct Answer: C

    Solution :

    We have,
    \[{{\sec }^{2}}(a+2)x+{{a}^{2}}-1=0\]\[\Rightarrow \]\[{{\tan }^{2}}(a+2)x+{{a}^{2}}=0\]
    \[\therefore \]\[\tan (a+2)x=0\]and \[a=0\]\[\Rightarrow \]\[\tan \,(2x)=0\]and \[a=0\]\[\Rightarrow \]\[2x=nx\]and \[a=0\]\[\Rightarrow \]\[x=\frac{nx}{2}\]and \[a=0\]
    \[x\in \,(-\pi ,\pi )\]
    \[\therefore \]\[x=0,\frac{\pi }{2},-\frac{\pi }{2}\]
    Number of ordered pair of \[(a,x)\] is 3. i.e. \[(0,0)\left( 0,\frac{\pi }{2} \right)\] and \[\left( 0,-\frac{\pi }{2} \right).\]


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