JEE Main & Advanced Mathematics Circle and System of Circles Question Bank System of circles

  • question_answer
    Consider the circles\[{{x}^{2}}+{{(y-1)}^{2}}=\] \[9,{{(x-1)}^{2}}+{{y}^{2}}=25\]. They are such that                                                   [EAMCET 1994]

    A)            These circles touch each other

    B)            One of these circles lies entirely inside the other

    C)            Each of these circles lies outside the other

    D)            They intersect in two points

    Correct Answer: B

    Solution :

               Centres and radii of the given circles are                    Centres: \[{{C}_{1}}(0,\ 1),\ {{C}_{2}}(1,\ 0)\]; Radii : \[{{r}_{1}}=3,\ {{r}_{2}}=5\].                    Clearly, \[{{C}_{1}}{{C}_{2}}=\sqrt{2}<({{r}_{2}}-{{r}_{1}})\]. Therefore one circle lies entirely inside the other.


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