Given three tetrahedrons (), planes () are drawn through respectively, and they are perpendicular to edges () respectively. Suppose that all nine planes () meet at a point , and points lie on line . Determine the intersection (shape and position) of the circumscribed spheres of the three tetrahedrons.
Solution
1. Understanding the Problem:
We are given three tetrahedrons (for ). For each tetrahedron, planes are drawn through respectively, and these planes are perpendicular to the edges respectively. All nine planes intersect at a common point . Additionally, points lie on a line .
2. Analyzing the Perpendicularity:
Since is perpendicular to , is perpendicular to , and is perpendicular to , the point must be such that:
This implies that is the orthocenter of the tetrahedron .
3. Circumscribed Sphere:
The circumscribed sphere of a tetrahedron is the sphere that passes through all four vertices of the tetrahedron. Given that is the orthocenter, the circumscribed sphere of has as its diameter. This is because the orthocenter and the circumcenter of a tetrahedron are related in such a way that the orthocenter lies on the diameter of the circumscribed sphere.
4. Intersection of Spheres:
Since lie on the line , and each sphere has as its diameter, the spheres intersect along a common circle. Let be the foot of the perpendicular from to the line . The diameter of the circle of intersection is , and this circle lies in the plane perpendicular to .
5. Conclusion:
The intersection of the circumscribed spheres of the three tetrahedrons is a circle with diameter in the plane perpendicular to the line .
The final answer is the circle with diameter in the plane perpendicular to the line .