CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2011

  • question_answer
    If\[\sin \theta =3\sin (\theta +2\alpha ),\]then the value of\[\tan (\theta +\alpha )+2\tan \alpha \]is

    A)  \[3\]                    

    B)         \[2\]

    C)  \[-1\]                   

    D)         \[0\]

    E)  \[1\]

    Correct Answer: D

    Solution :

    Given, \[\sin \theta =3\sin (\theta +2\alpha )\] \[\Rightarrow \] \[\frac{\sin \theta }{\sin (\theta +2\alpha )}=\frac{3}{1}\] Use componendo and dividendo formula, \[=\frac{\sin \theta +\sin (\theta +2\alpha )}{\sin \theta -\sin (\theta +2\alpha )}=\frac{3+1}{3-1}\] \[=-\frac{2\sin (\theta +\alpha ).\cos \alpha }{2\cos (\theta +\alpha ).\sin \alpha }=2\] \[\Rightarrow \]               \[-\tan (\theta +\alpha ).\cot \alpha =2\] \[\Rightarrow \]               \[\tan (\theta +\alpha )=-2\tan \alpha \] \[\Rightarrow \]               \[\tan (\theta +\alpha )=2\tan \alpha =0\]


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