An object of type Circle_3<Kernel> is a circle in the threedimensional Euclidean space ^{3}. Note that the circle can be degenerate, i.e. the squared radius may be zero.
Circle_3<Kernel> c ( Point_3<Kernel> const& center, Kernel::FT const& sq_r, Plane_3<Kernel> const& plane);  
introduces a variable c of type Circle_3<Kernel>.
It is initialized to the circle of center center and
squared radius sq_r in plane plane.
 
Circle_3<Kernel> c ( Point_3<Kernel> const& center, Kernel::FT const& sq_r, Vector_3<Kernel> const& n);  
introduces a variable c of type Circle_3<Kernel>.
It is initialized to the circle of center center and
squared radius sq_r in a plane normal to
the vector n.
 
Circle_3<Kernel> c ( Point_3<Kernel> const& p, Point_3<Kernel> const& q, Point_3<Kernel> const& r);  
introduces a variable c of type Circle_3<Kernel>.
It is initialized to the circle passing through the three points.
 
Circle_3<Kernel> c ( Sphere_3<Kernel> const& sphere1, Sphere_3<Kernel> const& sphere2);  
introduces a variable c of type Circle_3<Kernel>.
It is initialized to the circle along which the two spheres intersect.
 
Circle_3<Kernel> c ( Sphere_3<Kernel> const& sphere, Plane_3<Kernel> const& plane);  
introduces a variable c of type Circle_3<Kernel>.
It is initialized to the circle along which the sphere and the
plane intersect.
 
Circle_3<Kernel> c ( Plane_3<Kernel> const& plane, Sphere_3<Kernel> const& sphere);  
introduces a variable c of type Circle_3<Kernel>.
It is initialized to the circle along which the sphere and the
plane intersect.

Point_3<Kernel> const&  c.center () const  returns the center of c. 
Kernel::FT const&  c.squared_radius () const  returns the squared radius of c. 
Plane_3<Kernel> const&  c.supporting_plane () const  returns the supporting plane of c. 
Sphere_3<Kernel> const&  c.diametral_sphere () const  returns the diametral sphere of c. 
Kernel::FT const&  c.area_divided_by_pi () const  returns the area of c, divided by π. 
double const&  c.approximate_area () const  returns an approximation of the area of c. 
Kernel::FT const&  c.squared_length_divided_by_pi_square () const  
returns the squared length of c, divided by π^{2}.  
double const&  c.approximate_squared_length () const  
returns an approximation of the squared length (i.e. perimeter) of c. 
bool  c.has_on ( Point_3<Kernel> const& p) const 
bool  operator == ( const& c1, const& c2)  
returns true, iff c1 and c2 are equal, i.e. if they have the same center, the same squared radius and the same supporting plane.  
bool  operator != ( const& c1, const& c2)  
Bbox_3  c.bbox () const  returns a bounding box containing c. 