JEE Main & Advanced Mathematics Complex Numbers and Quadratic Equations Question Bank Geometry of complex numbers

  • question_answer
    PQ and PR are two infinite rays. QAR is an arc. Point lying in the shaded region excluding the boundary satisfies  [IIT Screening 2005]

    A) \[|z-1|>2;|\arg (z-1)|\,<\frac{\pi }{4}\]

    B) \[|z-1|>2;|\arg (z-1)|\,<\frac{\pi }{2}\]

    C) \[|z+1|>2;|\arg (z+1)|\,<\frac{\pi }{4}\]

    D) \[|z+1|>2;|\arg (z+1)|\,<\frac{\pi }{2}\]

    Correct Answer: C

    Solution :

      Equation of ray PQ \[\arg (z+1)=\frac{\pi }{4}\] Equation of ray PR \[\arg (z+1)=-\frac{\pi }{4}\] Shaded region is \[\frac{-\pi }{4}<\arg (z+1)<\frac{\pi }{4}\] \[|\arg (z+1)|<\frac{\pi }{4}\];   \[|PQ|=\sqrt{{{(\sqrt{2})}^{2}}+{{(\sqrt{2})}^{2}}}=2\] |PA| =2; |PR| = 2 so, arc QAR is of a circle of radius 2 unit with centre at \[P(-1,0)\]. All the points in the shaded region are exterior to this circle\[|z+1|=2\].


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