JEE Main & Advanced Sample Paper JEE Main Sample Paper-35

  • question_answer
    Statement 1: Consider two curves \[{{C}_{l}}:z\overline{z}+i\overline{z}+b=0\] and \[(b\in R,z=x+iy\] and \[i=\sqrt{-1})\]. where\[(b\in R,\,z=x+iy\] and \[i=\sqrt{-1}\]). If \[{{C}_{1}}\] and \[{{C}_{2}}\] intersects orthogonally then\[b=-2\].
    Statement 2:  If two curves intersects orthogonally then the angle between the tangents at all their points of intersection is\[\frac{\pi }{2}\].

    A)  Statement-1 is true, Statement-2 is true and Statement-2 is correct explanation for Statement-1.                              

    B)  Statement-1 is true, Statement-2 is true and Statement-2 is NOT the correct explanation for Statement-1.

    C)  Statement-1 is true, Statement-2 is false.

    D)  Statement-1 is false, Statement-2 is true

    Correct Answer: D

    Solution :

    \[{{C}_{1}}\,:z\bar{z}+iz\,-i\,\bar{z}+b=0\]             Put \[z=x+iy\]             \[{{x}^{2}}+{{y}^{2}}\,+i(x+yi)-i(x-iy)+b=0\]             \[\Rightarrow \,{{x}^{2}}+{{y}^{2}}\,-2y+b=0\]                      ?(1)             Also \[z\bar{z}+(1-i)\,z+(1+i)\,\bar{z}-4=0\] \[\Rightarrow \,\,{{x}^{2}}+{{y}^{2}}\,+(1-i)\,(x+iy)\,+(1+i)\,(x-iy)\,-4=0\]   \[\Rightarrow \,\,{{x}^{2}}+{{y}^{2}}\,+2x+2y-4=0\]                       ?(2) \[\therefore \] Using condition of orthogonally, we get \[2(0\times 1+(-1)(1))\,=b-4\,\Rightarrow \,-2=b-4\Rightarrow \,b=2\]         \[\therefore \,\,S-1\] is false, but S-2 is true.


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