 The set of all points in 3 dimensional space which are at a fixed distance r from a fixed point A(a,b,c) is a sphere. The center of the sphere is A and the radius is r.
 The equation of the sphere is (x  a)^{2} + (y  b)^{2} + (z  c)^{2} = r^{2}.
 The general equation of the sphere is x^{2} + y^{2} + z^{2} + 2ux + 2vy + 2wz + d = 0. Its center is (u, v, w) and radius is √(u^{2} + v^{2} + w^{2} d). The equation is a equation of a real sphere if (u^{2} + v^{2} + w^{2} d) ≥ 0
 The equation of a sphere passing through two points (x  x_{1})(x  x_{2}) + ((y  y_{1})(y  y_{2}) + (z  z_{1})(z  z_{2}) = 0
