The document discusses 3D shapes and objects. It defines 2D and 3D shapes, with examples like triangles and cubes. It explains how 3D objects can be formed by combining unit cubes. It also discusses how 3D shapes are represented on 2D surfaces like paper through techniques like isometric dots. The document classifies 3D shapes as polyhedral and non-polyhedral based on whether they have flat faces. It provides examples of different types of 3D solids like prisms and pyramids, describing their characteristics. It also discusses nets, edges, faces and vertices of 3D objects.

1. Introduction
We are living in a 3-dimensional space. Some of the objects around us are in 3
dimensional shape. We can differentiate 2-D shapes from 3-D shapes by observing
them. A triangle, square, rectangle are plane figures of 2-dimensions. While a
cube, cuboids are solid objects with 3 dimensions.
3-D Objects made with cubes: We can form solid shapes by arranging
four unit cubes. If we observe them from different positions, it seems to be
different, but the object is the same. Similarly if a solid is viewed from different
directions it appears in different shapes.
Representation of 3-D figures on 2-D: We used to draw 3-D figures on
2-D paper. Here we are able to represent only two dimensions on the plane paper,
the third dimension is only our imagination. In order to overcome this problem we
use isometric dots paper, in which we can represent length, breadth and height
with exact measurement of 3-D solid objects.

2. Various Geometrical Solids:In our surroundings we see various solid
objects. Among them some solid objects have 0 and some solid objects have flat
faces. Based on this property we can classify 3-D shapes as polyhedral and non-
polyhedral.
Various Geometrical Solids: Those solid objects have only flat surfaces
then the solid objects are called polyhedral.
Various Geometrical Solids: Those solid objects have only flat surfaces
then the solid objects are called polyhedral. Those solid objects have curved faces
then the solid objects are called non-polyhedral.
Regular Polyhedral: If two objects faces are congruent and all their edges are
equal and vertices are formed by an equal number of edges. Such type of solid
objects are called regular polyhedral.

3. Faces, Edges and Vertices of 3D-Objects: The living hall walls,
windows, tables and boxes, faces are flat faces. The flat faces meet at its edges. Two
or more edges meet at corners. Each corner is called vertex.
Prism and Pyramid: The solid object with two parallel and congruent
polygonal faces and lateral faces as rectangles or parallelograms is called a "prism".
A solid object whose base is a polygon and its lateral faces are triangular faces is
called "pyramid". A prism or pyramid is named after its shape of parallel and
congruent polygonal faces or the base.
Triangular Prism: If two congruent and parallel faces are triangular and its
lateral faces are parallelograms then it is known as triangular prism.
Triangular Pyramid: A pyramid whose base is a triangle is called a triangular
pyramid and it is also known as tetrahedron.

4. Net Diagrams: A net is a sort of skeleton - outlined in 2-D, which, when folded
the net results in 3-D shape. We can make prisms and pyramids by using net
diagrams.
Number of Edges, Faces and Vertices of polyhedrons: When we
count the number of faces, edges and vertices of a polyhedron.
we can conclude that F+V=E+2
Here F = Number of Faces;
V = Number of Vertices;
E = Number of Edges
This relationship is called "Euler's relation" for polyhedral. The relation was first
observed by the mathematician Leonhard Euler.