Unit A: Geometry

Chapter 1: Polygons

Angle Properties of Polygons

What property makes a shape a triangle? Hint: What makes a tricycle, a tricycle and not a bicycle? The triangle, is the smallest member, according to number of sides, of the polygon family.

A polygon is a closed shape made by straight sides. Polygons can have as few as three sides (a triangle) and the number of sides has no upper limit, though naming becomes difficult. Can you think of other polygon shapes? (Search naming polygons online to find more names for polygons!)

Many polygons are found in nature. For example, cutting an apple across its core reveals a star shape produced by the carpels (where the seeds are stored) that becomes a polygon if you connect the points. Connect the points of many starfish to see more pentagons,or another polygon, depending upon how many arms the starfish has.

In Ireland, hexagons are found in a region called Giant's Causeway. The unique basalt columns in this area were caused by volcanic eruptions that cooled very slowly.