CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2010

  • question_answer
    The value of \[tan\text{ }40{}^\circ +tan\text{ }20{}^\circ +\sqrt{3}\text{ }tan\text{ }20{}^\circ tan\text{ }40{}^\circ \]is equal to

    A)  \[\sqrt{12}\]                     

    B)  \[\frac{1}{\sqrt{3}}\]

    C)  1                            

    D)         \[\frac{\sqrt{3}}{2}\]

    E)  \[\sqrt{3}\]

    Correct Answer: E

    Solution :

    We know that, \[tan\text{(}20{}^\circ +40{}^\circ )=\frac{\tan 20{}^\circ +\tan 40{}^\circ }{1-\tan 20{}^\circ \tan 40{}^\circ }\] \[\Rightarrow \] \[\sqrt{3}=\frac{\tan 20{}^\circ +\tan 40{}^\circ }{1-\tan 20{}^\circ \tan 40{}^\circ }\] \[\Rightarrow \] \[\sqrt{3}-\sqrt{3}\tan 20{}^\circ \tan 40{}^\circ \]                                                 \[=\tan 20{}^\circ +\tan 40{}^\circ \] \[\Rightarrow \] \[\tan 20{}^\circ +\tan 40{}^\circ +\sqrt{3}\tan 20{}^\circ \tan 40{}^\circ \]                                 \[=\sqrt{3}\]


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