# Polygons

A polygon is just a “many sided shape”. A regular polygon is one where all the angles and sides are the same (if they are different you have an irregular polygon).

Names Of Regular Polygons

• 3 sided – equilateral triangle
• 4 sided – square
• 5 sided – pentagon
• 6 sided – hexagon
• 7 sided – heptagon
• 8 sided – octagon
• 9 sided – nonagon
• 10 sided – decagon

Even if this does not come up directly in the exam, it might help you in pub quizzes later in life.

Interior and Exterior Angles Interior angles are just the angles inside a shape, the exterior angles are the angles between the shape and the adjacent angle if a side was extended outwards….that sounds complicated but it’s pretty easy if you look at the diagram above.

There are some rules about these that apply to ANY POLYGON:

• The sum of the exterior angles is 360°
• The sum of the interior angles is (n – 2) x 180 ° – where n is the number of sides

There are some rules that apply only to REGULAR POLYGONS:

• Any given exterior angle equals 360° divided by n
• Any interior angle equals 180° minus the exterior angle