What are 2D shapes?
2D shapes are everywhere!
For example, windows are usually shaped like rectangles and clocks are shaped like circles.
2D shapes are flat and all have different properties.
Watch: Identifying polygons
Properties of 2D shapes
A property is a quality that a shape has. Examples of shape properties are:
- number of sides
- number of vertices (corners)
- length of sides
- types of angles (acute, obtuse, right-angle)
- perpendicular and parallel lines
Here are three 2D shapes. What properties do they have?
Triangles
All triangles have 3 sides and 3 angles.
Their internal angles add up to 180掳.
However, different triangles have different properties, depending on how they are drawn.
The types of triangle are:
- isosceles
- equilateral
- scalene
- right-angled
Quadrilaterals
A quadrilateral is a shape with 4 sides and 4 angles.
These are some examples of quadrilaterals and their properties:
Rectangle
2 pairs of equal sides.
Angles all right-angles (perpendicular lines).
2 pairs of parallel lines.
Square
A special type of rectangle.
Sides all equal length.
Angles all right-angles (perpendicular lines).
2 pairs of parallel lines.
Trapezium
1 pair of parallel lines.
2 sets of equal angles.
2 lines equal length and 2 that aren鈥檛.
Kite
2 pairs of equal sides.
1 pair of equal angles.
No parallel lines.
Regular polygons
These are shapes that have all equal sides and equal angles.
Pentagon
- 5 equal sides and angles.
Hexagon
6 equal sides and angles.
3 pairs of parallel lines.
Heptagon
- 7 equal sides and angles.
Octagon
8 equal sides and angles.
4 pairs of parallel lines.
Irregular polygons
These are shapes that have sides and angles of different sizes.
You can always identify the polygon by how many sides it has, eg. a pentagon is always a shape that has 5 sides.
Example:
This irregular pentagon has sides and angles that are different lengths and sizes.
It has two right angles and one pair of equal sides. The other 3 sides are different lengths.
Activity 1
Activity 2
2D shape hunt
Let's see what 2D shapes we can find around the house.
You will need a pencil and a piece of paper.
Look around the house for 2D shapes. Draw them on your piece of paper.
Can you draw and label:
- the sides
- the vertices
Quiz
Quiz 2
Quiz 3
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