JEE Main & Advanced JEE Main Paper (Held On 12 May 2012)

  • question_answer
    The area of the triangle whose vertices are complex numbers z, iz, z + iz in the Argand diagram is     JEE Main Online Paper (Held On 12 May 2012)

    A) \[2|z{{|}^{2}}\]                

    B)                        \[1/2|z{{|}^{2}}\]

    C)                        \[4|z{{|}^{2}}\]                

    D)                        \[|z{{|}^{2}}\]  

    Correct Answer: B

    Solution :

                    Vertices of triangle in complex form is z, iz, z + iz In cartesian form vertices are (x,y),(-y,x) and (x-y,x+y) So,\[y=-\frac{1}{2}x\pm \sqrt{2}\] \[\therefore \]Area of triangle \[=\frac{1}{2}\left| \begin{matrix}    x & y & 1  \\    -y & x & 1  \\    x-y & x+y & 1  \\ \end{matrix} \right|\] \[=\frac{1}{2}[x(x-x-y)-y(-y-x+y)+1\] \[(-yx-{{y}^{2}}-{{x}^{2}}+xy)]\] \[=\frac{1}{2}[-xy+xy-{{y}^{2}}-{{x}^{2}}]=\frac{1}{2}({{x}^{2}}+{{y}^{2}})\] (\[\because \] Area can not be negative) \[=\frac{1}{2}{{\left| z \right|}^{2}}\left( \because z=x+iy,{{\left| z \right|}^{2}}={{x}^{2}}+{{y}^{2}} \right)\]


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