CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2007

  • question_answer
    If\[f(x)=\frac{{{\log }_{e}}(1+{{x}^{2}}\tan x)}{\sin {{x}^{3}}},x\ne 0\]is to be continuous at\[x=0,\]then\[f(0)\]must be defined as

    A)  1                                            

    B)  0

    C)  1/2                       

    D)         \[-1\]

    E)  2

    Correct Answer: A

    Solution :

    \[f(x)=\frac{{{\log }_{e}}(1+{{x}^{2}}\tan x)}{\sin {{x}^{3}}}\] This function is continuous at\[x=0,\]then \[\underset{x\to 0}{\mathop{\lim }}\,\frac{{{\log }_{e}}(1+{{x}^{2}}\tan x)}{\sin {{x}^{3}}}=f(0)\] \[\Rightarrow \]\[\underset{x\to 0}{\mathop{\lim }}\,\frac{{{\log }_{e}}\left\{ 1+{{x}^{2}}\left( x+\frac{{{x}^{3}}}{3}+\frac{2{{x}^{5}}}{15}+..... \right) \right\}}{{{x}^{3}}-\frac{{{x}^{9}}}{3!}+\frac{{{x}^{15}}}{5!}-....}\] \[\Rightarrow \]\[\underset{x\to 0}{\mathop{\lim }}\,\frac{{{\log }_{e}}(1+{{x}^{3}})}{{{x}^{3}}-\frac{{{x}^{9}}}{3!}+\frac{{{x}^{15}}}{5!}-....}=f(0)\] [on neglecting higher power of\[x\]in\[{{x}^{2}}tan\text{ }x\]] \[\Rightarrow \]\[\underset{x\to 0}{\mathop{\lim }}\,\frac{{{x}^{3}}-\frac{{{x}^{6}}}{2}+\frac{{{x}^{9}}}{3}-.....}{{{x}^{3}}-\frac{{{x}^{9}}}{3!}+\frac{{{x}^{15}}}{5!}-....}=f(0)\] \[\Rightarrow \]               \[1=f(0)\]


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