JHS1 Mathematics · Term 2 Week 11: Shape and Space

Lesson notes

Learning Objectives

Indicator: B7.3.1.2.3 - Copy and bisect angles

By the end of the lesson, learners can:

Copy a given angle accurately using a pair of compasses and a ruler, following the steps of drawing a ray, transferring the arc, and joining the final point.
Bisect a given angle by constructing the angle bisector with compasses and a ruler, and label the two resulting equal angles correctly.
Verify the accuracy of a copied or bisected angle by measuring with a protractor and comparing angle sizes.
Identify whether a given diagram shows a correct or incorrect angle bisector by checking whether the bisector passes through the vertex and divides the angle into two equal parts.
Apply the skill of copying and bisecting angles to solve practical problems involving equal divisions of angles.

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Curriculum details

Strand: Geometry and Measurement (Strand 3)
Sub-strand: Shape and Space (3.1)
Content standard: B7.3.1.2 - Demonstrate how to construct a perpendicular to a line from a given point, bisect a line, bisect angles, and construct angles of the following sizes: 30˚, 45˚, 60˚, 75˚
Indicator: B7.3.1.2.3 - Copy and bisect angles
Suggested placement: Term 2, Week 11 (Week 23 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, Common Core Programme (JHS1-JHS3), 2023, p. 53
Transcribed from the official NaCCA publication. Check this page against the source.

Exemplars (from the NaCCA curriculum)

E.g.1: Use a pair of compasses and a ruler to copy a given angle A, (i.e. draw a line and locate point B; copy the arc ST and transfer using B as the centre to obtain VW;join B and W to obtain the copied angle.

Figure from the jhs1 mathematics curriculum, printed page 53

E.g.2 Perform geometric construction to bisect a given angle (∠BOA) to obtain the two equal angles∠BOC and COA.

Figure from the jhs1 mathematics curriculum, printed page 54

(i) Sketch any acute angle and label it ABC.
(ii) Copy the angle, measure and record its value.
(iii) Sketch any angle and ask a colleague to copy the angle.
E.g. 3 Which of the angles has a correct angle bisector?