1TH/vwo Ch13 Symmetry

• Wiskunde
• Middelbare school
• havo
• Leerjaar 3

Symmetry (p. 80)

What you need:

- Textbook, writingbook, iPad

- Pen, pencil, geotriangle

- Calculator

Schoolbags in the cuboard

Phones in the phonebag

Bluetooth 

- ON

- VPN off

Lesson goal

Identify the axis of symmetry, and point of symmetry of a shape.

Lets start by 

revising 

some shapes

What special figure is this?

1. Equilateral triangle
2. Acute triangle
3. Isosceles triangle
4. Obtuse triangle

What special figure is this?

1. Trapezium
2. Parallelogram
3. Rectangle
4. Kite

What special figure is this?

1. Trapezium
2. Parallelogram
3. Rectangle
4. Kite

What is symmetry?

Symmetry

... being made up of exactly similar parts 

facing each other or 

around an axis.

Is this shape symmetrical?

1. Yes
2. No
3. could be both
4. Dont know

Is this shape symmetrical?

1. Yes
2. No
3. could be both
4. Dont know

Is this shape symmetrical?

1. Yes
2. No
3. could be both
4. Dont know

There are two types of symmetry

Line symmetry: Figures are symmetrical about a line, the axis of symmetry.

Symmetrical about a point

Such figures have a point of symmetry and can be rotated to be found symmetrical.

Line symmetry

Symmetrical about a point

Complete the sentence. This shape is ...

1. Line symmetrical
2. Point symmetrical
3. Not symmetrical
4. Dont know

Complete the sentence. This shape is ...

1. Line symmetrical
2. Point symmetrical
3. Not symmetrical
4. Dont know

Complete the sentence. This shape is ...

1. Line symmetrical
2. Point symmetrical
3. Not symmetrical
4. Dont know

Now try 12 a and c

12 a How many axes of symmetry does a rhombus have?

1. 1
2. 2
3. 3
4. 4

12c) Does it have a point of symmetry?

1. Yes
2. No

Try on your own

1, 2, 5 and 7

TRY ON YOUR OWN...

RULES:

• In your writingbook
• Use: Textbook
• Discussion when you are stuck is allowed

Extra excercise: M2 and M3 (p. 96)

Challenge: C2 (p. 98)

nr

13, 14

p. 81

Conclusion

Line symmetry: Figures are 

symmetrical about a line, the 

axis of symmetry.

 Some object can be rotated 

around a point of symmetry  

to be found symmetrical.