JEE Main & Advanced Mathematics Complex Numbers and Quadratic Equations Question Bank Conjugate, Modulus and Argument of complex number

  • question_answer
    \[arg\,(5-\sqrt{3}i)=\]

    A) \[{{\tan }^{-1}}\frac{5}{\sqrt{3}}\]

    B) \[{{\tan }^{-1}}\left( -\,\frac{5}{\sqrt{3}} \right)\]

    C) \[{{\tan }^{-1}}\frac{\sqrt{3}}{5}\]

    D) \[{{\tan }^{-1}}\left( -\frac{\sqrt{3}}{5} \right)\]

    Correct Answer: D

    Solution :

    Let  \[z=5-\sqrt{3}\,i\] Þ   \[r(\cos \theta +i\sin \theta )=5-\sqrt{3}\,i\] Þ  \[r\cos \theta =5\]and \[r\sin \theta =-\sqrt{3}\] \[\therefore \]  \[\tan \theta =-\frac{\sqrt{3}}{5}\Rightarrow \theta ={{\tan }^{-1}}\left( -\frac{\sqrt{3}}{5} \right)\]


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