
 
compute the squared radius of the circle passing through the points
$$p, $$q, and $$r. Precondition: $$p, $$q, and $$r are not collinear.  

 
compute the squared radius of the smallest circle passing through $$p, and $$q, i.e. one fourth of the squared distance between $$p and $$q.  

 
compute the squared radius of the sphere passing through the points $$p,
$$q, $$r and $$s. Precondition: $$p, $$q, $$r and $$s are not coplanar.  

 
compute the squared radius of the sphere passing through the points $$p, $$q, and $$r and whose center is in the same plane as those three points.  

 
compute the squared radius of the smallest circle passing through $$p, and $$q, i.e. one fourth of the squared distance between $$p and $$q. 