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Mathematics Matters Lesson Accounts 45 - Angles of a Polygon


This page has been archived. The content was correct at the time of original publication, but is no longer updated.
Created on 29 May 2008 by ncetm_administrator
Updated on 17 June 2008 by ncetm_administrator

 
Mathematics Matters Lesson Accounts
A collection of memorable mathematics lessons that conference and colloquia delegates had observed or taught which they felt were successful.  Each account refers to one or more of the values and principles in the report.
 

Lesson Account 45 - Angles of a Polygon

Written by Richard Deakin
Organisation Failsworth School
Age/Ability Range Year 9 level 5/6 students
 
 

How was the session/task introduced?
Task to build on knowledge of external angles of a polygon. This came after lesson on internal angles. Teacher explained what external angle was. The main task was to create an irregular polygon with an even number of sides. with three exterior angles of 90°, 60°, 90°, and the remaining exterior angles being equal. Pupils asked (i) how many sides could the polygon have, (ii) to work out the missing angles and make sketches of what the different polygons could look like.

How was the session/task sustained?
Pupils discussed how many sides polygon had. Small groups sketched shape on plan paper. An absolute mess was created with pupils’ attempts.

How was the session/task concluded?
Successful solution was obtained by pupils and shared with other groups.

What were the critical moments?
When pupils realised that internal + external angle = 180°, so if external angle was 120°, the internal angle must be 60°. Once pupils deduced the 3 internal angles the solution became easier to obtain.

What mathematics was learnt? (on plan and off plan) and what is the evidence of learning?
Strengthened knowledge of polygons, internal and external angles

How was that mathematics learnt?
Through deductive reasoning. The initial task helped pupils to understand external and internal angle = 180°, and external angles in polygon added to 360°, .

Other memorable outcomes
Solutions displayed on classroom walls.

Resources
RM Kaleidos maths alive http://www.learningplatform.rm.com/,
Y9 core SSM1 lesson 7 (tasks based from task in this product).

 
 

Downloadable PDF

Click here to download this lesson account in PDF format.
 
 

Values & Principles

Strategies for investigation and problem solving
Makes appropriate use of whole class interactive teaching, individual work and cooperative small group work
Uses rich, collaborative tasks
 
 

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Lesson Accounts Introduction

Mathematics Matters - What constitutes the effective learning of mathematics? find out more

 

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Comments

 


06 November 2014 01:38
the lesson is interesting. I would love to teach in my class.
By heylhi1234
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