JEE Main & Advanced Mathematics Complex Numbers and Quadratic Equations Question Bank De Moivre's theorem and Roots of unity

  • question_answer
    The value of i1/3 is [UPSEAT 2002]

    A) \[\frac{\sqrt{3}\,+i}{2}\]

    B) \[\frac{\sqrt{3}\,-i}{2}\]

    C) \[\frac{1+i\sqrt{3}}{2}\]

    D) \[\frac{1-i\sqrt{3}}{2}\]

    Correct Answer: A

    Solution :

      \[{{i}^{1/3}}={{\left( \cos \frac{\pi }{2}+i\sin \frac{\pi }{2} \right)}^{1/3}}=\cos \frac{\pi }{6}+i\sin \frac{\pi }{6}\]\[=\frac{\sqrt{3}}{2}+\frac{i}{2}\].


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