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Details of Class: Lesson 1
Date:
Time: 50mins
Learning Intentions/Topic:
Year: 8
Geometry: Triangles
To recognise different types of triangles and
their properties
To be able to draw all different types of
triangles, labelling sides and angles correctly
Room:
No. of students:
Relationship to VELS:
Classification of polygons with reference to a
definition or key property
Using language relevant to the topic
Resources Required:
Students to each have their own workbook and stationery
Maths Quest 8 textbook
Student Activities worksheet/questions (attached)
Matches or item of similar size (15 per student)
Introduction/Housekeeping/Warm-up:
Introduction to Geometry:
Who knows what Geometry is?
Pg. 234 text – geometry comes from Latin geo meaning earth and metre meaning measure.
Considered geometry as a science of measuring our Earth and describing its properties. Geometry
today looks at angles, shapes and solids, and investigates their relationships and properties.
5 mins
Content
Resources
Time
What is a triangle?
- 3 sides: tri means three. Triangle = three angles
- ‘Give Way’ signs
- Identify other everyday triangle-shaped things
2 min
There are different types of triangles. Triangles can be named
according to the length of their sides or the size of their angles.
Go through ‘Naming Triangles’ together as class describing types
of triangles and their properties.
Classification:
What is a right-angle? A. An angle of 90°
What is an acute angle? A. Angle less than 90°
What is an obtuse angle? A. Angle greater than 90°
7 min
Text p.235
Important note: To indicate the sides of equal length and angles
of equal size, we use identical marks. To indicate that the angle is
right (90°), a small square is used.
*Draw examples on whiteboard and point out symbols/markings
that are used and what they mean.
Activity: Students to complete table of triangles from ‘Student
Activity’ sheet with the help of the information on p. 235
Get students to draw certain types of triangles on the board
using correct side and angle markings where appropriate. Allow
students to explain the drawing to their classmates, and allow
classmates to help if student is unsure.
3 min
‘Student Activity’
sheet – triangle table
10 min
6 mins
Students to complete activities 2-5 from question sheet.
‘Student Activity’
Hand out matches (or similar) to students to allow them to
complete questions 4, 5 and extensions.
Students can work in pairs for these match stick tasks although
all students must copy answers into each of their workbooks.
Matches
14 min
Reinforcement of Ideas/Questioning/Homework:
Collect matches
Homework is to complete any questions which were not finished in class. If you do not have
any matches at home to help complete questions, use pens, pencils, cutlery, or other similar
objects instead.
3 mins
Overall reflection of lesson:
Student Activities:
Triangles
1. Complete the table. Keep completed table for your own reference.
Picture
Name of Triangle
Definition
Equilateral Triangle
One angle is greater than 90°
Scalene Triangle
All angles are less than 90°
Student Activities:
2. Using side and angle markings where appropriate, draw a triangle that is:
a) Right-angled
b) Isosceles
c) Obtuse-angled
d) Scalene
3. Using side and angle markings where appropriate, draw a triangle that is:
a) Both right-angled and scalene
b) Both acute-angled and isosceles
c) Both obtuse-angled and isosceles
d) Both acute-angled and equilateral
(Students can work on their own or in pairs for the following activities)
4. Using 12 matches, construct each of the following triangles. Draw the solutions in your
workbook, clearly showing the number of matches used on each side.
a) An equilateral triangle
b) A scalene triangle
c) An isosceles triangle
5. Use matches to construct each of the following structures. Draw the solutions in your
workbook.
a) Use 9 matches to make 3 equilateral triangles
b) Use 8 matches to make 3 equilateral triangles
c) Use 7 matches to make 3 equilateral triangles
d) Use 12 matches to make 6 equilateral triangles
*Note: A match can be used as a common side between two triangles
Extension activities (if time):
1. Using 15 matches:
a) Construct as many different isosceles triangles as you can. Draw your solutions, clearly
showing the number of matches used on each side of each triangle.
b) Construct as many different scalene triangles as you can. Draw your solutions, clearly
showing the number of matches used
2. Using 6 matches, construct four equilateral triangles. All triangles must have side lengths of
one match.
Answers:
Triangles
1. Complete the table. Keep completed table for your own reference.
Picture
Name of Triangle
Definition
Isosceles Triangle
Two equal sides;
Two equal angles
Equilateral Triangle
All sides equal;
All angles equal
Obtuse-angled triangle
One angle is greater than 90°
Right-angled triangle
Has one right angle
Scalene Triangle
All sides different;
All angles different
Acute-angled triangle
All angles are less than 90°
Answers:
4. a) 4,4,4
b) 3,4,5
c) 5,5,2
5. a)
b)
c)
c)
Extension activities:
1. a) Three isosceles triangles: 4,4,7; 6,6,3; 7,7,1.
b) Three scalene triangles: 2,6,7; 3,5,7; 4,5,6.
2.
A tetrahedron (four triangular faces)