JEE Main & Advanced JEE Main Paper (Held on 09-4-2019 Morning)

  • question_answer All the points in the set \[S=\left\{ \frac{\alpha +i}{\alpha -i}:\alpha \in R \right\}\left( i=\sqrt{-1} \right)lie\]on             [JEE Main 9-4-2019 Morning]

    A) circle whose radius is 1.

    B) straight line whose slope is 1.

    C) straight line whose slope is -1

    D) circle whose radius is \[\sqrt{2}\].

    Correct Answer: A

    Solution :

    Let\[\frac{\alpha +i}{\alpha -i}=z\]\[\Rightarrow \]\[\frac{\left| \alpha +i \right|}{\left| \alpha -i \right|}=\left| z \right|\]\[\Rightarrow \]\[1=\left| z \right|\] \[\Rightarrow \]circle of radius 1

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