Two-dimensional Shapes have dimensions in only 2 directions - a width and a length.

Plane Shapes - Same as 2-dimensional shapes; The word plane means flat because these shapes are on flat surfaces

Polygons - 2D shapes with straight sides e.g. triangle, rectangle

Regular Polygons - Polygons with all sides of equal length e.g. equilateral triangle and square

Types of Polygons

NUMBER OF SIDES

NAME OF POLYGON

3

triangle

4

quadrilateral

5

pentagon

6

hexagon

7

heptagon

8

octagon

9

nonagon

10

decagon

11

undecagon un- = 1 deca- = 10

12

dodecagon do- = 2 deca- = 10

Did You Know That...?

Most names for 2D shapes and 3D solids come from the Greek language.

Many 2D shapes have names ending in -gon. Many 3D solids have names ending in -hedron.

Hept- is Greek for "seven". Sept- is Latin for "seven".

Types of Triangles

DIAGRAM

NAME OF TRIANGLE

PROPERTIES

Right-angled triangle

Has one angle of 90° Longest side is called the hypotenuse

Equilateral triangle

3 sides are equal 3 angles are equal Each angle is 60°

Isosceles triangle

2 sides are equal 2 angles are equal

Scalene triangle

No sides are equal No angles are equal

Types of Quadrilaterals

PARALLELOGRAM

Opposite sides parallel

Opposite sides equal

Opposite angles equal

Diagonals bisect each other

RHOMBUS

Opposite sides parallel

Opposite sides equal

Opposite angles equal

All sides equal

Diagonals equal

Diagonals bisect each other

Diagonals meet at right angles

Diagonals bisect the angles at the vertices (corners)

RECTANGLE

Opposite sides parallel

Opposite sides equal

Opposite angles equal

All sides equal

Diagonals equal

Diagonals bisect each other

SQUARE

Opposite sides parallel

Opposite sides equal

Opposite angles equal

All sides equal

All angles equal

Diagonals equal

Diagonals bisect each other

Diagonals meet at right angles

Diagonals bisect the angles at the vertices (corners)

TRAPEZOID

Opposite sides parallel (one pair only)

Diagonals bisect each other

KITE

2 pairs of sides equal but not opposite sides equal

1 pair of opposite angles equal

1 diagonal bisects the other diagonal

Diagonals meet at right angles

1 diagonal bisects one pair of angles

Questions - What am I?

Q1. I have 3 sides of equal length.

Q2. I have 4 equal sides, my diagonals bisect each other and the angles, and none of my angles are right angles.

Q3. I have 2 pairs of equal sides, my diagonals are not equal, my diagonals meet each other at right angles, and one pair of my opposite angles is equal.