1. Triangles and Quadrilaterals
Level 4/5 Booster
Lesson 8B
Triangles and Quadrilaterals

2. rotational symmetry parallel opposite quadrilateral external angle
Objectives:
To identify and use the properties of triangles and quadrilaterals.
Vocabulary:
parallel
rotational symmetry
opposite
quadrilateral
external angle
congruent

3. Name the quadrilaterals and state their identifying properties:
W/S 8.1B

4. Parallelogram
Opposite sides equal
Opposite sides parallel
No lines of symmetry
Rotational symmetry order 2

5. Rectangle
Opposite sides equal (and parallel)
All angles 90º
Two lines of symmetry
Rotational symmetry of order 2

6. Rhombus
All sides equal
Opposite sides parallel
Two lines of symmetry
Rotational symmetry of order two
Isosceles trapezium
One pair of equal sides
One pair of parallel sides
A line of symmetry
No rotational symmetry

7. Square
Trapezium
Four equal sides
One pair of opposite sides parallel
All angles 90º
No lines of symmetry
Four lines of symmetry
No rotational symmetry
Rotational symmetry of order 4

8. You need W/S 8.2B
Using a 3 by 3 pinboard draw as many different triangles as you can find.
Example
These two triangles are the same (congruent) – one is a translation of the other.
These two triangles are the same (congruent) – one is a rotation of the other.

9. Here are the 8 different triangles that are possible.

10. Which of these triangles have an obtuse angle?

11. Which of these triangles are isosceles?

12. Which of these triangles contain a right angle?

13. ˆ Conventional labelling: A B
The marked angle is angle ADC or angle CDA.
Sometimes written as <ADC
or ADC D ˆ C
How would you describe the angle indicated in the same way? A B C D
Estimate the size of angle BAD. º
What type of angle is angle ADC?
Obtuse

14. A B C
AB has been extended to point D.
Angle CBD (marked) is an external angle of the triangle. D
Follow these instructions:
Draw a triangle and label the vertices A, B and C.
Extend line BC to the point D and label point D.
What do you know about the angles ACD and ACB?
Angles ACD and ACB are on a straight line and therefore have a sum of 180º.

15. You have two congruent right-angled triangles
You have two congruent right-angled triangles. What different quadrilaterals can you make by putting sides of equal length together?
Example:
parallelogram
Using two congruent right-angled triangles what other shapes can you make?

16. Here are the quadrilaterals you can find.
Other shapes you can produce are:

17. rotational symmetry parallel opposite quadrilateral external angle
Objectives:
To identify and use the properties of triangles and quadrilaterals.
Vocabulary:
parallel
rotational symmetry
opposite
quadrilateral
external angle
congruent

18. Thank you for your attention