# 3 DIMENSIONS

3 Dimensions Shapes Are Geometric Figures that have 3 Dimensions : 1. Length 2. Width and 3. Depth . They differ from 2D Shapes because they have Thickness . There are Two main Types Of 3Dimensions Shapes : A. Polydhedra B. Non - Polyhedra . Polyhedron comes from the Greek : Poly means " Many "and Hedra means " Faces ". Many Faces . Polyhedra is The Plural of Polyhedron.

Polyhedra : Are 3D Shapes with Flat Faces, like Cubes and Prisms.

Non - Polyhedra : When One of The Faces is not Flat. Like Spheres, Cones and Cylinders .

The CUBE ( 6 Faces ) or Hexahedron is a Regular Polyhedron and one of the Platonic Solids . The very Famous Greek Philosopher Plato believed that since All objects are 3 Dimensional their Atoms must be in the shape of Regular Polyhedra . Some other Regular Polyhedra are The Octahedron with 8 Faces. The Dodecahedron ( 12 Faces ) . All Its Faces are Pentagonals, representing The Atom COSMOS. The Icosahedron, 20 Faces, representing Water .

CUBOID

A Cuboid is a convex polyhedron, bounded by Six Quadrilateral Faces .

# Euler Characteristic x ( Greek letter chi )

Any Convex Polyhedra's Surface, has Euler Characteristic : x = V + E - F = 2 . V, E and F are respectively the numbers of Vertices, Edges and Faces .

VOLUME

If The Dimensions of a CUBOID are X, Y and Z, Its Volume is XYZ. The Product of The Lenght, Height and Debth .

SURFACE AREA

If The Dimensions of a CUBOID are A, B and C, The Surface Area is 2AB + 2AC + 2BC .