# 1718 WB1Z CH11 Lesson 1

Recap CH5
- Parallel and perpendicular lines
-  Right, acute and obtuse angles
- Measuring and drawing angles and distances
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Slide 1: Slide
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This lesson contains 14 slides, with text slides and 5 videos.

Lesson duration is: 50 min

## Items in this lesson

Recap CH5
- Parallel and perpendicular lines
-  Right, acute and obtuse angles
- Measuring and drawing angles and distances

#### Slide 1 -Slide

Parallel lines
Lines a and b are parallel to each other.
Lines c, d and e are parallel to each other.

Notation:

#### Slide 2 -Slide

Perpendicular lines
Lines s and t are perpendicular to each other.

Notation:

#### Slide 3 -Slide

Angles & Degrees
A right angle is 90°
An acute angle is between 0° and 90°
An obtuse angle is between 90° and 180°

right angle                       acute angle                                  obtuse angle
90°                                       between 0° and 90°                  between 90° and 180°

#### Slide 9 -Video

Symmetry
There are two types of symmetry:
- Reflection symmetry
- Rotation symmetry
Figures can have no symmetry, one type of symmetry or two types of symmetry.

#### Slide 10 -Slide

Reflection symmetry
If a figure could be folded in half, so both halves fit exactly on top of each other, we say a figure has reflection symmetry.
The line on which you would fold the figure is called the axis of symmetry.

#### Slide 11 -Slide

Rotation symmetry
If a figure can be rotated less half a turn or less and fit exactly on themselves again, we say a figure has rotation symmetry.
If a figure fits onto itself after a quarter, a half and three quarters of a turn, we say it has rotation symmetry through 90°, 180° and 270°.

120° and 240°                                                      60°, 120°, 180°, 240° and 300°

#### Slide 12 -Slide

Rotation symmetry
This figure has 7 identical parts, so 1/7th of
a turn will make it fit onto itself again.

The figure has rotation symmetry through

7360°=5173°
5173°,10276°,15472°,20575°,25771°,30874°

#### Slide 13 -Slide

Homework Tuesday
Chapter 11, make and correct:
R3, R5, R6, 2, 3, 4, 5, 6, 7, 8