CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2004

  • question_answer
    If\[\sin \left( \frac{\pi }{4}\cot \theta  \right)=\cos \left( \frac{\pi }{4}\tan \theta  \right)\]then\[\theta \]is equal to:

    A)  \[2n\pi +\frac{\pi }{4}\]                               

    B)  \[2n\pi \pm \frac{\pi }{4}\]

    C)  \[2n\pi -\frac{\pi }{4}\]

    D)         \[n\pi -\frac{\pi }{4}\]

    E)  \[n\pi +\frac{\pi }{4}\]

    Correct Answer: E

    Solution :

    \[\sin \left( \frac{\pi }{4}\cot \theta  \right)=\cos \left( \frac{\pi }{4}\tan \theta  \right)\] \[\Rightarrow \]               \[\sin \left( \frac{\pi }{4}\cot \theta  \right)=\sin \left( \frac{\pi }{2}-\frac{\pi }{4}\tan \theta  \right)\] \[\Rightarrow \]               \[\frac{\pi }{4}(\tan \theta +\cot \theta )=\frac{\pi }{2}\] \[\Rightarrow \]               \[{{\tan }^{2}}\theta +1-2\tan \theta =0\] \[\Rightarrow \]               \[{{(\tan \theta -1)}^{2}}=0\] \[\Rightarrow \]               \[\tan \theta =1=\tan \frac{\pi }{4}\] \[\Rightarrow \]               \[\theta =n\pi +\frac{\pi }{4}\]


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