Definitions:
1. 1) A polyhedron is a solid whose surface consists of flat polygons.
2. 2 )A face is a flat surface of a solid.
3. 3)An edge is a line where two faces meet.
4. 4)A vertex is a point where three or more faces meet.
5. 5)A diagonal is a line joining two vertices which is not an edge. A diagonal may go through the solid or be an its surface.
CUBOID
A cuboid is a box shape with faces that are rectangles. The diagram show a cuboid ABCDEFGH. All are rectangles that are parallel or perpendicular to each other.
-AG and BG are diagonals. AG goes through the solid, and GB lies on its surface.
CUBE
-A cube is a cuboid with all edges the same length. All the faces are squares.
PRISM
-A prism is a solid which has the same cross- section through. A triangular prism has a triangular cross-section
Faces: 5
Edges: 9
Vertices: 6
PYRAMID
A pyramid has a flat base in the shape of a polygons and all other edges come to a point called the vertex
TYPES OF PYRAMID
1.
-If the vertex of the pyramid is above the centre of the base it is a right pyramid.
EXERCISE 3.1B
1. 1) Find everyday objects in the shape of
(a) a cuboid (b) a cube (c) a prism
2. 2)What are the mathematical names for the shapes of these objects?
(a) a match box (b) a football (c) an unsharpened pencil (d) the tip of a sharpened pencil.
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