# math

### 3D Geometry

**3D Geometry **

3 Dimensional Geometry- An object that has height, width and depth, like any object in the real world. Example: your body is three-dimensional **http://www.mathsisfun.com/definitions/three-dimensional.html**

Polyhedron- A solid with flat faces (from Greek poly- meaning "many" and -edron meaning "face"). Example: pyramids and prisms Each flat surface (or "face") is a polygon

Non-Polyhedra- (if any surface is not flat)

prism is a polyhedron, which means the cross section will be a polygon (a straight-edged figure) ... so all sides will be flat! **http://www.mathsisfun.com/geometry/prisms.html**

PYRIMID A solid object where: * The base is a polygon (a straight-sided shape) * The sides are triangles which meet at the top (the apex). It is a polyhedron. This is a square pyramid, but there are also triangular pyramids, pentagonal pyramids. **http://www.mathsisfun.com/definitions/pyramid.html**

CONE-A solid (3-dimensional) object that has a circular base and one vertex

SPHERE A solid object with: * two identical flat ends that are circular or elliptical * and one curved side. It has the same cross-section from one end to the other. â€˘Sphere Factsâ€˘ Notice these interesting things: It is perfectly symmetrical It has no edges or vertices (corners It is not a polyhedral All points on the surface are the same distance from the center

TORUS It can be made by revolving a small circle along a line made by another circle. It has no edges or vertices It is **not** a polyhedron **http://www.mathsisfun.com/geometry/torus.html** (*All images came from ***http://www.google.com/imghp**)