Teacher notes

• Revise the features of polygons with students.
  To be a polygon a shape must:
  •  be 2-D
  •  be closed (i.e. the sides of the polygon all meet without gaps)
  •  have only straight sides.
  For example, circles and ovals are not polygons because they have curved sides.
• Students will be classifying categories within categories. Students should be familiar with sub-categories relating to the number of sides (triangles, quadrilaterals). The new sub-category for polygons introduced in this chapter are regular and irregular polygons. Both types are included in the student book and printable masters and students are encouraged to draw these as well in question 3 in Activity 1 of this section.
• A square is also a rectangle and a rhombus. A rectangle has four sides and four right angles and a square therefore fits this description. A rhombus has four equal sides and opposite angles that are equal and a square also fits this description. You could discuss this with students to extend their understanding of these sub categories.
• The trapezium (plural: trapezia or trapeziums, are a four sided shape with only one set of parallel sides) is introduced in the student text and may be new to some students.
  Students should also be encouraged to use the correct mathematical term rhombus (plural: rhombi or rhombuses, have four sides of equal length and opposite sides are parallel and opposite are equal) rather than ‘diamond’.
• Previously right angles have been described as square corners. Having students use a “square corner” to identify “right angles” around the classroom will help students to make this connection.
• Student ‘What shape am I?’ puzzles (page 241) and pictures from the practical (page 243), could be collated into a wall display, class ‘book’ or digital presentation.