Question 193146
The locus of points that are equi-distant from a given point (a, b, c) in 3-dimensional space (a sphere) is given by:
{{{d = sqrt((x-a)^2+(y-b)^2+(z-c)^2)}}} Square both sides.
{{{d^2 = (x-a)^2+(y-b)^2+(z-c)^2}}} but the distance is called the radius, r, so...
{{{highlight(r^2 = (x-a)^2+(y-b)^2+(z-c)^2)}}}