Modern Pure Solid Geometry

altitude antiparallel bimedians bisecting planes bisectors centers of similitude centroid circumcenter circumsphere coaxal pencil coincides collinear coplanar Corollary corresponding DABC diameter dihedral Euler line Find the locus four given spheres four lines four spheres given line given point given tetrahedron harmonic conjugate hedron hence the proposition homothetic hyperbolic group isoclinal lines isodynamic points isodynamic tetrahedron isogonal isosceles tetrahedron Lemoine point line of centers line of intersection lines joining medians meets mid-point oblique circular cone opposite edges opposite faces orthic orthocentric group orthocentric tetrahedron orthogonal sphere pairs of opposite parallel parallelepiped pencil of spheres plane ABC plane determined plane passing point with respect points of contact polar plane radical axis radical plane radii radius ratio S-abc segment skew lines skew quadrilateral sphere of similitude spheres of antisimilitude square symmedian symmetric tangent plane tetrahedron ABCD three lines three spheres triangle ABC trihedral angle trihedron vertex