The equation of director circle of the circle ${x^2} + {y^2} = {a^2},$ is
The equation of director circle of the circle ${x^2} + {y^2} = {a^2},$ is
- A
${x^2} + {y^2} = 4{a^2}$
- B
${x^2} + {y^2} = \sqrt 2 {a^2}$
- C
${x^2} + {y^2} - 2{a^2} = 0$
- D
None of these
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