CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2005

  • question_answer
    The equation to the circle with centre (2,1) and touching the line \[3x+4y=5\] is :

    A)  \[{{x}^{2}}+{{y}^{2}}-4y-2y+5=0\]

    B)  \[{{x}^{2}}+{{y}^{2}}-4x-2y-5=0\]

    C)  \[{{x}^{2}}+{{y}^{2}}-4x-2y+4=0\]

    D)  \[{{x}^{2}}+{{y}^{2}}-4x-2y-4=0\]

    Correct Answer: C

    Solution :

    Distance from centre (2, 1) to the line                 \[3x+4y-5=\]; Radius- of circle                 \[\Rightarrow \]               \[\frac{|3\,\,(2)+4\,(1)-5|}{\sqrt{{{3}^{2}}+{{4}^{2}}}}=r\]                 \[\Rightarrow \]               \[\frac{5}{5}=r\,\,\,\Rightarrow \,\,\,\,r=1\]                 \[\therefore \] Equation of circle is                 \[{{(x-2)}^{2}}+{{(y-1)}^{2}}={{1}^{2}}\]                 \[\Rightarrow \]               \[{{x}^{2}}+{{y}^{2}}-4x-2y+4+1=1\]                 \[\Rightarrow \]               \[{{x}^{2}}+{{y}^{2}}-4x-2y+4=0\]


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