11/11/2007: Circle meeting (Dimitri Shlyakhtenko)Geometry in three dimensions. The focus of the circle meeting will be on threedimensional objects, such as cubes, pyramids, prisms and so on.
Before coming to the circle meeting, try to solve the following problem. Draw a tetrahedron ABCD with A the top vertex and B,C,D the three bottom vertices. Pick a point each on the line segments AB, AC and CD. Let us call these points X, Y and Z. The plane through X, Y, Z intersects the tetrahedron in some way. Can you find the lines formed by the intersections of the faces of the tetrahedron with that plane? Handouts:[Edit]

