49. What condition does a triangular pyramid satisfy that the projection of its vertex on the bottom is the perpendicular of the triangle on the bottom?
1. The three sides are perpendicular to the opposite bottom
2. The three sides are vertical
RELATED INFORMATIONS
- 1. In a triangular pyramid a-bcd, the projection of D in plane ABC is e, and the projection of a in plane BCD is f (1) If de intersects AF, verify that ad is perpendicular to BC (2) Is the inverse proposition of (1) Tenable
- 2. In the triangular pyramid abc-a1b1c1, AB is perpendicular to AC, the projection of vertex A1 on the bottom ABC is exactly point B, and ab = AC = A1B = 2 Find the angle between Aa1 and ABC (2) Determine a point P on edge b1c1 so that AP = 14 under the root sign, and calculate the cosine value of dihedral angle p-ab-a1 Answer 2 under the root sign 5 / 5 Newspapers 20-5
- 3. What is the volume of a square with a volume of 8 if its vertices are on the sphere?
- 4. The ratio of the volume of a cylinder to the volume of a sphere is 3:2. Then the ratio of the side area of the cylinder to the surface area of the sphere is () A. 1:1B. 1:2C. 2:3D. 3:2
- 5. If the vertices of a square whose edge length is 2cm are all on a sphere, then the volume of the sphere is
- 6. What's the volume ratio between the inscribed ball and the circumscribed ball of a cube? I think the radius of the circumscribed ball is two-thirds root
- 7. The volume ratio of the inscribed ball to the circumscribed ball of the cube is, pro, to be explained in detail
- 8. If the total area of a cube is 24, then the volume of its circumscribed sphere is______ .
- 9. Let the surface area of a cube be 24. What is the volume of its inscribed sphere
- 10. The surface area of cube with edge length a is equal to___ ; volume equal to___ The radius of its circumscribed ball is___ The volume of its circumscribed sphere is___
- 11. Proof: if the projection from the vertex of a triangular pyramid to the bottom is the perpendicular center of the bottom triangle, then the projection from any vertex of the bottom triangle to the opposite side must also be the perpendicular center of the triangle
- 12. Using Euler's formula, think about a polyhedron with 10 faces, 30 edges and 20 vertices
- 13. A polyhedron has 20 vertices and 30 edges. It has () faces. This geometry is ()
- 14. Fill in the table according to the number of faces, vertices and edges of the polyhedron shown in the figure below. What rules do you find?
- 15. According to Euler's formula, think about a polyhedron with 10 faces, 30 edges and 20 vertices?
- 16. Is there a polyhedron with 10 faces, 30 edges and 20 vertices? (hint: complete according to Euler formula.)
- 17. A polyhedron with 12 vertices and 20 faces. How many edges is this polyhedron As above
- 18. If a polyhedron has 12 edges and 6 vertices, then it is a polyhedron______ The surface of the body
- 19. If a polyhedron has 12 edges and 6 vertices, then it is a polyhedron______ The surface of the body
- 20. Euler, a great mathematician, discovered and proved the formula about the relationship between the vertex (V), the number of edges (E) and the number of faces (f) of a polyhedron______ .