A Dead Parrot?

Despite what you may think a polygon is not a dead parrot (Polly gone…geddit?). A polygon is just a fancy name for any flat shape (also known as a 2-dimensional shape) which is made by drawing straight lines which all join together.

Each type of polygon has its own name (which unfortunately you'll need to remember) and the ones which are most commonly seen are shown in the table below:

Number of Sides

Name of Polygon

How to remember the name

3

Triangle

The name says that the shape has 3 angles (Tri is an old word for 3) - it also has 3 sides.

4

Quadrilateral

If someone gives birth to "Quads" - they have 4 babies - this shape has 4 sides

5

Pentagon

The number 5 looks like the letter S, put 5 in front of Pent and it looks like Spent - this shape has 5 sides

6

Hexagon

The word Six ends with the letter x and so does Hex (another old word which means six) - this shape has 6 sides

8

Octagon

An octopus has 8 legs - this shape has 8 sides

10

Decagon

The word Decompress has 10 letters and begins with Dec - this shape has 10 sides

 

If you can think up better ways of remembering these shapes please use them. Once you remember the stuff in the table above, answering basic questions about polygons is easy!

e.g. Name a quadrilateral.

(From remembering the table - this is a shape with 4 sides….. correct answers are: a square, or a rectangle or a parallelogram…etc.)

 

Polygons can be split into 2 types:

Regular Polygons and Irregular Polygons

A regular polygon has all sides of the same length (and all interior angles the same).

An irregular polygon can have sides of any length.

Once you know what an interior angle is, it will be no great surprise that the interior angles will all be the same for a shape where all the sides are of the same length. If you can't remember what an angle is here is an explanation.

An interior angle is simply the angle between two of the lines in a polygon. For example, you should know that ALL INTERIOR ANGLES in a triangle add up to 180o. If all the sides in a triangle are equal, then the three interior angles will be equal, as we know that they all add up to 180o all we do is divide 180 by 3 which gives a single interior angle of 60o.

Here are pictures of all the regular polygons:

So, a regular triangle is called an equilateral triangle and a regular quadrilateral is called a square.

If you find it difficult to remember equilateral - lateral thinking means "sideways thinking" and equi is used in the start of words for some thing meaning equal (e.g. equi-distant, equi-valent etc.) so equilateral simply means equal sided - this may help.

These two regular polygons are the only ones with fancy names. The others are simply called regular pentagon etc.

If someone asks you to give an example of an irregular quadrilateral - use rectangle.

If someone asks you to give an example of an irregular triangle there is another special name for a triangle which you could use - an isosceles triangle. This is a triangle with only 2 sides which have the same length. To remember this you could think of making an SOS call in the middle of iSOSceles. If O is one side the other two sides of the same length could be S and S. Here's an example of an isosceles triangle:

Any other irregular polygons can be any old shape as each side can be as long or as short as you want it to be!

Not too difficult so far I hope.

Easy Ways to Calculate Polygon angles