Circle
[li]Circle is a locus of points (set of points) in a plane, which are all equidistant from the center (0,0). The constant or equidistant
distance is called the radius. Symbolically, PC=r. which means any point from the locus of points (P) of the equation of circle to
the center (C) is always equal to radius (r).
k= Y axis
h= X axis
r= Radius