JCECE Engineering JCECE Engineering Solved Paper-2002

  • question_answer
    The centre of a circle \[(2,\,\,-3)\] and the circumference is \[10\pi \]. The equation or the circle is:

    A) \[{{x}^{2}}+{{y}^{2}}+4x+6y+12=0\]

    B) \[{{x}^{2}}+{{y}^{2}}-4x+6y+12=0\]

    C) \[{{x}^{2}}+{{y}^{2}}-4x+6y-12=0\]

    D)  \[{{x}^{2}}+{{y}^{2}}-4x-6y-12=0\]

    Correct Answer: C

    Solution :

    Let \[r\] be the radius of a circle. \[\therefore \]Circumference of a circle\[=10\pi \] \[\Rightarrow \]                                           \[2\pi r=10\pi \] \[\Rightarrow \]                                                \[r=5\,\,unit\] \[\therefore \]Equation of circle whose centre is \[(2,\,\,-3)\] and radius \[5\], is                 \[{{(x-2)}^{2}}+{{(y+3)}^{3}}={{5}^{2}}\] \[\Rightarrow \]               \[{{x}^{2}}+{{y}^{2}}-4x+6y+4+9=25\] \[\Rightarrow \]               \[{{x}^{2}}+{{y}^{2}}-4x+6y-12=0\]


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