J & K CET Engineering J and K - CET Engineering Solved Paper-2003

  • question_answer
    Which of the following is an odd function?

    A)  \[|x|+1\]

    B)  \[\sin x+\cos x\]

    C)  \[{{x}^{2}}\,\,\sec x+x\,{{\tan }^{2}}x\]

    D)  \[{{x}^{2}}\cot x+4{{x}^{4}}\,\text{cosec x+}{{\text{x}}^{5}}\]

    Correct Answer: D

    Solution :

    [a]  Let \[f(x)=|x|+1\] \[\therefore \] \[f(-x)=|-x|+1\] \[=f(x),\] even function [b] Let \[f(x)=\,\sin x+\cos x\] \[\therefore \] \[f(-x)=\sin \,(-x)+\cos (-x)\] \[=-\sin \,x+\,\cos \,x\] neither even nor odd function [c] Let  \[f(x)={{x}^{2}}\,\,\sec x+x\,{{\tan }^{2}}x\] \[\therefore \] \[f(-x)={{x}^{2}}\,\sec \,\,x-x\,{{\tan }^{2}}x\] neither even nor odd function [d] Let  \[f(x)={{x}^{2}}\,\cot \,x+4{{x}^{2}}\,\text{cosec x+}{{\text{x}}^{5}}\] \[\therefore \] \[f(-x)=-{{x}^{2}}\,\cot \,x-4{{x}^{4}}\,\text{cosec x-}{{\text{x}}^{5}}\] \[=-f(x),\] odd function Hence, option [d] is correct.


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