Plane Geometry · SHS1 Design And Communication…

Lesson notes

Learning Objectives

Indicator: 1.2.1.LI.3 - Blend circles and lines with arcs.

By the end of the lesson, learners can:

Explain what is meant by blending circles and straight lines with arcs in technical drawing.
Demonstrate the steps for drawing an arc that blends (joins) two straight lines smoothly.
Construct an arc that blends a straight line and a circle, and an arc that blends two circles.
Apply the principle of blending circles and straight lines with arcs to design a spanner in a mixed-gender group of 4.
Evaluate their finished spanner drawing against given assessment criteria, identifying strengths and areas for improvement.

This lesson builds directly on the types of plane figures covered in Week 1 (Indicator 1.2.1.LI.1) and the enlargement and division work done in Week 2 (Indicator 1.2.1.LI.2). The ellipse and Archimedean spiral in Weeks 4 and 5 will require the same careful use of drawing instruments practised here.

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Curriculum details

Strand: Geometry (Strand 2)
Sub-strand: Plane Geometry (2.1)
Content standard: 1.2.1.CS.1 - 1.2.1.CS.1 Apply the concept of plane geometry in designing. 1.2.1.LO.1 Use knowledge of plane geometry to draw plane geometrical shapes and design different artefacts based on plane geometrical figures.
Indicator: 1.2.1.LI.3 - Blend circles and lines with arcs.
Suggested placement: Semester 2, Week 3 (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: NaCCA curriculum document, p. 37

Exemplars (from the NaCCA curriculum)

Collaborative learning/ Group work: With the use of videos, charts, internet surfing, drawing instruments, and materials, demonstrate the blending of circles and straight lines with arcs.

Problem-based learning, collaborative learning/ Group work: Through mixed gender grouping of 4 each, guide learners to design a spanner using the principle of blending circles and straight lines with arcs.

Assessment (1.2.1.AS.3). The document marks these depth-of-knowledge levels for this indicator: Level 3 Strategic reasoning; Level 4 Extended critical thinking and reasoning.

Teaching and Learning Materials:
- Models
- Charts
- Reference books
- Drawing studio
- Drawing instruments
- Access to internet
- LCD Projector