CIRCLE

It is the set of all points in a plane that are equidistant from a fixed point in a plane. The fixed  point is called the centre. The fixed  distance is called  the radius
Standard Equation 
Equation of circle with  centre at (h, k) with radius r
(x-h)² + (y-k)²=r²
Note:
If the centre is at origin
Equation of circle =  x²+y²=r²
General equation of a circle is
x²+y²+2gx+2fy+c=0
with centre =(-g  -f) and radius is √(g²+f²⁻c)
*Find the equation of circle with (2, 3) and radius 8? 
(x-h)²+(y-g)²= r²
(x-2)²+(y+3)²=64
x²-4x+4+y²+6y+9=64
x²+y²-4x+6y-51=0

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