2. A plane with more than one point and only parallel to a known straight line. As we all know, there is only one plane parallel to a straight line in space.

3, on the plane, more than one point, and only on a straight line perpendicular to the known line; Space, with more than one line and only one known plane perpendicular to it.

4. The distance between the sides at any point in the interior is a given plane equilateral Δ ABC (such as the high side of Δ ABC); The front point of the bottom edge of isosceles ABC is determined by two waists apart (one waist high).

Space, the distance between each surface surrounded by any point of an object, is a constant value (tetrahedron); The distance between each side of the front point is a fixed value, which is the face (side height) of the bottom triangular pyramid.

Five stars, the plane of the triangle is parallel to the square of the corresponding side of the triangle, which is equal to the straight line and the original area of the triangle passing through its side? Ratio of; The spatial pyramid is a small pyramid whose lower surface is parallel to the plane, and the volume ratio of the original pyramid is equal to the corresponding prism-cube ratio.