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CBSE - VIII

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Visualising Solid Shapes

**Three dimensional objects **or **solids** generally have length, breadth and height. **Three dimensional objects **look different from different locations or angles.

A **polyhedron** is a solid shape bounded by **polygons** whereas **non-polyhedrons** do not have **polygon** shaped faces.

Cubes, cuboids, prisms, and pyramids are few examples of **polyhedrons**.

Spheres, cones and cylinders are a few examples of **non-polyhedrons**.

The **polygonal regions **forming the polyhedron are known as its **faces**, two intersecting faces meet at a line segment called an **edge** and three edges meet at a point called the **vertex**.

F+V=E+2 is known as **Euler’s formula **and it holds true for any **polyhedron**. Here F stands for faces, V for vertices and E for the edges of the **polyhedron**.

A **polyhedron** is said to be regular if its faces are made up of **regular polygons** and the same number of faces meet at each vertex.

An **irregular polyhedron **is made of** polygons **whose sides and angles are not of equal measure.

In a **convex polyhedron**, the line segment joining any two points on the surface of the **polyhedron** lies entirely inside or on the **polyhedron**.

A **polyhedron** some of whose plane sections are **concave polygons **is known as a **concave polyhedron**. **Concave polygons **have at least one interior angle greater than 180° and has some of its sides bent inward.

A prism is a **polyhedron** with parallel congruent polygon bases and sides made of parallelograms.

A **pyramid** is a **polyhedron** whose base is a **polygon** of any number of sides and whose lateral faces are triangles with a common vertex.

**Prisms** and** pyramids** are named after the shape of their base.

Maps represent the location of a place or object in relation to other places or objects.

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**F+V=E+2**** **