Properties of 2D Shapes

Properties of 2D shapes introduces students to key vocabulary used to describe the uniqe properties of 2D and 3D shapes.  This is a prerequisite unit before moving on to drawing 3D shapes in Term 2 of Year 9.  Learning progresses from describing 2D shapes to performing basic transformations such as rotations, enlargements, translations and reflections.


Properties of 2D Shapes Lessons

Prerequisite Knowledge

  • distinguish between regular and irregular polygons based on reasoning about equal sides and angles.
  • know angles are measured in degrees: estimate and compare acute, obtuse and reflex angles
  • draw 2-D shapes using given dimensions and angles

Success Criteria

  • use conventional terms and notations: points, lines, vertices, edges, planes, parallel lines, perpendicular lines, right angles, polygons, regular polygons and polygons with reflection and/or rotation symmetries; use the standard conventions for labelling and referring to the sides and angles of triangles; draw diagrams from written description
  • derive and apply the properties and definitions of: special types of quadrilaterals, including square, rectangle, parallelogram, trapezium, kite and rhombus; and triangles and other plane figures using appropriate language
  • identify and apply circle definitions and properties, including: centre, radius, chord, diameter, circumference, tangent, arc, sector and segment

Key Concepts

  • Understanding and using the vocabulary is key throughout this topic.
  • Regular polygons are closed shapes with straight lines of equal length.
  • Students need to recognise different types of quadrilaterals and triangles by their geometrical properties.
  • All shapes have a rotational symmetry of at least one.
  • Reflected vertices are an equal distance from the line of symmetry.

Common Misconceptions

  • Students often confuse the part of a circle.
  • Diagonal lines do not have to be slanted and can be horizontal or vertical.
  • A circle is not a polygon since its edge of not straight.
  • Rectangles are incorrectly assumed to have a rotational symmetry of order 4.

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