Lines and Shapes · B5 Mathematics

Lesson notes

Learning Objectives

Indicator: B5.3.1.1.3 - Prove that a polygon is regular by measuring the sides and angles or by folding and superimposing

By the end of the lesson, learners can:

Define a regular polygon as a polygon with all sides congruent and all angles congruent.
Distinguish regular polygons (equilateral triangle, square, regular pentagon, regular hexagon) from irregular polygons by inspecting sides and angles.
Prove that a polygon is regular by measuring all sides with a ruler and all angles with a protractor.
Prove that a polygon is regular by folding it and superimposing sides and angles to check congruence.
Justify their conclusion (regular or irregular) with evidence from measurements or folding.

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Curriculum details

Strand: Geometry and Measurement (Strand 3)
Sub-strand: Lines and Shapes (3.1)
Content standard: B5.3.1.1 - Identify and sort quadrilaterals, including rectangles, squares, trapezoids, parallelograms, and rhombuses, according to their attributes
Indicator: B5.3.1.1.3 - Prove that a polygon is regular by measuring the sides and angles or by folding and superimposing
Suggested placement: Term 3, Week 2 (Week 26 of the year)
Our suggestion, laid out in curriculum order across three terms of twelve weeks. NaCCA does not fix the week, so follow your school's scheme of learning.
Curriculum reference: Mathematics Curriculum for Primary Schools (Basic 4-6), 2019, p. 96
Transcribed from the official NaCCA publication. Check this page against the source.

Exemplars (from the NaCCA curriculum)

E.g. 1 Give learners foldable cut-out 2D quadrilaterals - rectangles, squares, trapezoids, parallelograms, and rhombuses - to investigate the properties in terms of sides, angles, and diagonals and complete the table Properties Rectangle Square rhombuses trapezoids parallelograms Sides All sides are congruent No Yes Opposite sides are congruent Opposite sides are parallel Angle Opposite angles are congruent All angles are right angles Diagonals Diagonals bisect each other Diagonals are congruent Diagonals meet at right angles