Recognising 2D Shapes
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.
Properties are the qualities that a shape has. Examples of shape properties are:
- number of sides
- number of angles (corners)
- length of sides
- types of angles (acute, obtuse, right-angle)
- perpendicular and parallel lines
Take a look at these shapes and their properties:
Triangles
All triangles have 3 sides and 3 angles.
However, different triangles have different properties, depending on how they are drawn. You have to look very carefully to see what is different.
For example, compare these two triangles:
Like all triangles, both have 3 sides and 3 angles.
However, the yellow triangle’s sides are all the same length and the angles are all the same size.
The green triangle has a right-angle and all the sides are a different length.
Quadrilaterals
A quadrilateral is a shape with 4 sides and 4 angles.
These are some examples of quadrilaterals and their properties:
Square
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Sides all equal length.
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Angles all right-angles (perpendicular lines).
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2 pairs of parallel lines.
Rectangle
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2 sides longer than the others.
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Angles all right-angles (perpendicular lines).
-
2 pairs of parallel lines.
Trapezium
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1 pair of parallel lines.
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2 sets of equal angles.
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2 lines equal length and 2 that aren’t.
Kite
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2 pairs of equal sides.
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1 pair of equal angles.
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No parallel lines.
Regular polygons
These are shapes that have all equal sides and equal angles.
Pentagon
- 5 equal sides and angles.
Hexagon
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6 equal sides and angles.
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3 pairs of parallel lines.
Heptagon
- 7 equal sides and angles.
Octagon
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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, e.g. 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.
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