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PYRAMID

December 18, 2007

प्य्रामिद ऎंड sphere

Pyramid and Spheres
Pyramids are polyhedra because they are made up of plane faces. Spheres are not polyhedra because they are curved.

Pyramids
If a line that is fixed at a point, called the vertex, is moved around the perimeter of a polygon, then a pyramid is formed.

The following solid is pyramid.



Pyramids are named after their base. So, the pyramid shown above is an example of a rectangular pyramid.

Some other pyramids are shown below.



A pyramid is said to be right when its vertex is directly above the centre of the base. The cross-sections parallel to the base are the same shape but have different sizes.




The net of the above pyramid consists of:

a rectangular base; and
four triangular faces


Note:
The cross-sections parallel to the base have the same shape as the base but different sizes.
The net of a pyramid consists of a base polygon and a number of triangular faces.
A regular pyramid has a base that is a regular polygon and has faces which are isosceles triangles.

Spheres
If a semicircle is revolved about its diameter, then a sphere is formed.

The following solid is a sphere.



The cross-sections...

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Tags: creation


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