A circle is the locus of a point which moves in such a way that its distance from a fixed point is always constant.

**Circles**

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**1. The equation of a circle when the centre and radius are given.**

Let *C*(*h*, *k*) be the centre and ‘*r*’ be the radius of the circle

Let P(*x*, *y*) be any point on the circle

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**2. Equation of a circle when the end points of a diameter are given**

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**3. General equation of a circle**

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**4. Parametric form of a circle**

Consider a circle with radius r and centre at the origin. Let *P* (*x*, *y*) be any point on the circle. Assume that *OP* makes an angle *i*with the positive direction of *x*-axis.

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**5. Tangents**

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**Length of the tangent to the circle**

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11th Business Mathematics and Statistics(EMS) : Chapter 3 : Analytical Geometry : Circles | Definition, equation, Formula, Solved Example Problems, Exercise | Mathematics