What 2D shapes should I know?

• You should know the general names of all the 2D polygons
• A polygon is a flat (plane) shape with n straight sides
• A triangle has 3 sides
• A quadrilateral has 4 sides
• A pentagon has 5 sides
• A hexagon has 6 sides
• A heptagon has 7 sides
• An octagon has 8 sides
• A nonagon has 9 sides
• A decagon has 10 sides

• You should know the names and properties of the different types of triangles
• An equilateral triangle has 3 equal sides and 3 equal angles
• An isosceles triangle has 2 equal sides and 2 equal angles
• A right triangle has one 90° angle
• You should know the names and properties of the different types of quadrilaterals
• These are squares, rectangles, parallelograms, rhombuses, trapeziums and kites 
• You should know the names and properties of circles and circle parts

What are the properties of rectangles and squares?

• Rectangles and squares have four equal right angles (90°)
• Rectangles have two pairs of equal, parallel sides
• Squares are just regular rectangles, all four of their sides are equal
• The diagonals of a rectangle bisect each other at the centre of the rectangle
• This means that they cut each other in half
• There will be two pairs of angles at this point
• For a rectangle, one pair of obtuse angles and one pair of acute angles
• For a square, all four angles will be equal to 90°
• Pythagoras’ theorem can be used to find the length of the diagonal of a square or rectangle

What are the properties of parallelograms and rhombuses?

• Parallelograms and rhombuses (rhombi) have two pairs of equal, opposite, angles
• Parallelograms and rhombuses have two pairs of opposite, parallel sides
• Rhombuses have four sides of the same length
• Rhombuses are also parallelograms, but they are not regular as they do not have four equal angles
• A square is a regular rhombus
• The diagonals of a parallelogram bisect each other, forming two pairs of opposite angles
• The diagonals of a rhombus bisect each other at right angles (90°)
• This means that they cut each other in half
• The diagonals will not be of equal length

What are the properties of trapeziums?

• Trapeziums have one pair of opposite, parallel sides
• These are not of equal length
• Trapeziums may not have any equal angles
• As with all quadrilaterals, the angles add up to 360°
• If a trapezium has a line of symmetry, it is classed as isosceles
• Isosceles trapeziums have two pairs of equal angles
• The non-parallel sides in an isosceles trapezium will be equal length
• An isosceles trapezium has two diagonals of equal length

What are the properties of kites?

• Kites have one line of symmetry, known as their main diagonal
• The angles opposite the main diagonal are equal
• The diagonals of a kite bisect each other at right angles (90°)
• This means that they cut each other in half
• The diagonals will not be of equal length
• Kites have no parallel sides
• Kites have two pairs of equal, adjacent sides

What are the properties of circles?

• Circles are different to other 2D shapes and you must be familiar with their vocabulary
• For example, a circle’s perimeter is called a circumference and its line of symmetry is called a diameter
• The ratio