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In this video you will learn about common Geometric Shapes

All about shapes

Let’s take a look at many of the geometric shapes you will encounter in geometry classes.

We will begin with 2d shapes which have length and width, but no height.

2d shapes include polygons and curved shapes.

3d shapes have height, width, and depth.

These shapes can have straight lines or curves.

Let’s get started by looking at our first type of 2d shapes “polygons”

Polygons are 2-dimensional closed shapes.

A closed shape does not have any openings, and all of the lines connect.

You can’t leave the inside of a closed shape without crossing a line.

Polygons have straight lines and do not have curves

A polygon has three parts.

Straight Lines

Vertices which are the point at which the lines intercept

Angles are formed by intercepting lines

There are several types of polygons

A regular polygon has equal lines and angles

An irregular does not have equals lines and angles

A concave polygon has one angle greater than 180 degrees

A convex polygon does not have any internal angles greater than 180 degrees

A simple polygon does not have any lines that cross over.

A complex polygon has at least one line that crosses over itself

Polygon names

Named after the number of sides and angles

Triangle 3 sides

Quadrilateral

Pentagon 5

Hexagon 6

Heptagon 7

Octagon 8

Nonagon 9

Decagon 10

Hendecagon 11

Dodecagon 12

After 12 sides it is acceptable to give the number of sides and then gon

For example 14 gon has 14 sides

Curved 2d shapes have curved lines instead of straight lines.

Common examples of curved shapes include a circle,

an ellipse which looks like a circle that has been stretched or squashed

A crescent is also a curved 2d shape

3d shapes are shapes that have height, width and depth

A sphere and a cone are examples of 3d shapes

Many 3d shapes are considered polyhedrons.

Let’s take a look at the properties of polyhedrons

A polyhedron is a 3D solid figure in which each side is a flat surface composed of polygons.

What is a polyhedron?

A polyhedran is a 3D solid figure with a flat surface.

A polyhedran does not have any curved surfaces.

Polyhedron is derived from poly=many.

Hedron = Face so it means many faced geometric shape.

Is a Dodacahedron a polyhedron yes

Is a triangle a polyhedron? No is is only 2D

Is a sphere a polyhedron? No it has curves

Is a coffee mug a polyhedron? No

Some common examples of polyhedron are prisms and pyramids

Euler's Polyhedron states that the number of faces + number of vertices = number of edges + 2

A platonic solid is a convex Polyhedron that satisfy these three characteristics

All are regular polygons

All faces are congruent

All corners are congruent. The same number of faces meet at every vertex

3 Platonic solids are made of equilateral triangles

tetrahedron, octahedron, icosahedron

One platonic solid is made of squares

One platonic solid is made of pentagons

Cube 3 squares at each corner

6 square faces

Tetrahedron

3 equilateral triangles at each corner

4 triangle faces

Octahedron

4 equilateral triangles at each corner

8 triangle faces

Icosahedron

5 equilateral triangles at each corner

20 triangle faces

Dodecahedron

3 pentagons at each corner

12 pentagon faces

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Tagged under: geometric shapes,plane shapes,polygons,polyhedrons,circle,square,properties,2d shapes,3d shapes,shapes

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