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If x2 + y2 - 4x - 4y - k = 0 is the equation of the locus of the point from which perpendicular tangents can be drawn to the circle x2 + y2 - 4x - 4y = 0, then the value k is ....... |
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Answer» The equation x2 + y2 - 4x - 4y = 0 ...(i) represents a circle with centre (2, 2) and radius √8 = 2√2 . Then the locus of point from which perpendicular tangents can be drawn to the circle given in Eq. (1) is a concentric circle whose radius is 2 times the radius of the circle [this circle is called the director circle of the circle given in Eq. (1). Hence, the radius of the director circle is √2(2√2) = 4. Thus k = 8. |
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