JEE Main & Advanced Sample Paper JEE Main Sample Paper-14

  • question_answer
    The number of solution(s) of the equation \[\cos \frac{\pi x}{3\sqrt{3}}={{x}^{2}}+4-2x\sqrt{3}\] will be

    A)  1                                            

    B)  2                 

    C)  infinitely many                

    D)  0

    Correct Answer: D

    Solution :

                    \[\cos \,\frac{\pi x}{3\sqrt{3}}={{x}^{2}}-2\sqrt{3}\,x+3+1\] \[\cos \,\frac{\pi x}{3\sqrt{3}}={{(x-\sqrt{3})}^{2}}+1\] \[\because \]     \[{{(x-\sqrt{3})}^{2}}+1\ge 1\] and        \[\cos \,\frac{\pi x}{3\sqrt{3}}\le 1\] For \[x=\sqrt{3},\,\,\cos \,\,\frac{\pi x}{3\sqrt{3}}\,=\cos \,\frac{\pi }{3}\,=\frac{1}{2}\] and \[{{(x-\sqrt{3})}^{2}}+1=1\]


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