11th Class Mathematics Sample Paper Mathematics Olympiad - Sample Paper-8

  • question_answer
    \[\underset{x\to 0}{\mathop{Lt}}\,\frac{{{e}^{{{x}^{2}}}}-\cos x}{{{x}^{2}}}\]is

    A)  \[\frac{2}{3}\]                         

    B)  \[\frac{1}{2}\]              

    C)  \[\frac{3}{2}\]                         

    D)  2

    Correct Answer: C

    Solution :

    [c] \[\underset{x\to 0}{\mathop{\lim }}\,\frac{{{e}^{x}}-\cos x}{{{x}^{2}}}\]       which is \[\frac{0}{0}\]form \[=\underset{x\to 0}{\mathop{\lim }}\,\frac{{{e}^{{{x}^{2}}}}.2x+\sin x}{2x}\]  [By L' Hospital Rule] Which is \[\frac{0}{0}\]form \[=\underset{x\to 0}{\mathop{\lim }}\,\frac{2.{{e}^{{{x}^{2}}}}+4{{x}^{2}}.{{e}^{{{x}^{2}}}}\cos x}{2}\]            [By L' Hospital Rule] Applying limit\[x\to 0\], we have \[=\frac{2\times 1+0+1}{2}=\frac{3}{2}\]


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