JCECE Engineering JCECE Engineering Solved Paper-2003

  • question_answer
    If \[z=x+iy\], then the area of a triangle whose vertices are points \[z,\,\,iz\] and \[z+iz\] is:

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

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

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

    D)  \[\frac{3}{2}|z{{|}^{2}}\]

    Correct Answer: B

    Solution :

    Since,    \[z=x+iy\] \[\therefore \]  \[iz=-y+xi\] and        \[z+iz=x+iy+i(x+iy)\]                 \[=(x-y)+i(x+y)\] Since, \[z+iz\] and \[z+iz\] are the vertices of a triangle. \[\therefore \]  Area of triangle\[=\frac{1}{2}\left| \left| \begin{matrix}    x & y & 1  \\    -y & x & 1  \\    x-t & x+y & 1  \\ \end{matrix} \right| \right|\] \[=\frac{1}{2}|[x(x-x-y)-y(-y-x+y)\] \[+1(-xy-{{y}^{2}}-{{x}^{2}}+xy)]|\] \[=\frac{1}{2}|[-xy+xy-{{y}^{2}}-{{x}^{2}}]|\] \[=\frac{1}{2}[{{x}^{2}}+{{y}^{2}}]\] \[=\frac{|z{{|}^{2}}}{2}\]


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