 # Polygons 1

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## Polygons 1

#### Definitions and names

A polygon is simply a closed 2-dimensional shape made up of straight lines. The word itself actually means 'many-sided shape'.

Obviously, the polygon with the least number of sides is the triangle.

Here are the names of all the polygons with up to 12 sides: #### Triangles

Triangles can be classified using their sides or their angles.

The angles in a triangle always add up to 1800.

#### Special types of triangle

Equilateral - All 3 sides equal and all 3 angles equal (to 600).

Isosceles - Two sides the same and the angles at the bottom of those sides are equal.

Scalene - No sides or angles equal.

You can also classify triangles by their angles :

Acute-angled - All angles are acute (less than 900).

Right-angled - One angle is 900.

Obtuse-angled - One angle is obtuse (greater than 900).

#### Area

The area of a triangle is However, you must use the perpendicular height. That means at 900 to the base. ### New & unique from S-cool 