# 1718 WB1Z CH11 Lesson 4

Which exercises/theory should I discuss on the board?
1 / 12
Slide 1: Woordweb
WiskundeMiddelbare schoolvwoLeerjaar 1

In deze les zitten 12 slides, met interactieve quizzen en tekstslides.

Lesduur is: 50 min

## Onderdelen in deze les

Which exercises/theory should I discuss on the board?

#### Slide 1 -Woordweb

Sum of the angles
The sum of the three angles in a triangle is 180°
The sum of the four angles in a quadrilateral is 360°

A+B+C=180°
D+E+F+G=360°

#### Slide 2 -Tekstslide

Why is the sum of the angles in a triangle 180°?
You can watch the proof here:
(You do not have to know the proof)
(Khan Academy also has lots of interactive practice exercises!)

#### Slide 3 -Tekstslide

Calculating angles
You can use the sum of the angles and your knowledge of special triangles and quadrilaterals to calculate unknown angles.

#### Slide 4 -Tekstslide

Calculating angles
Calculate the size of angle C.

#### Slide 5 -Tekstslide

What size is angle C?
A
C=3608260=218°
B
C=82+60=142°
C
C=1808260=38°
D
C=3(82+60)=37°

#### Slide 6 -Quizvraag

Calculating angles
The angle sum of a triangle is 180°

C=1808260=38°

#### Slide 7 -Tekstslide

Calculating angles
Quadrilateral DEFG is a rhombus.
Calculate the size of angle G.

#### Slide 8 -Tekstslide

What size is angle G?
A
G=245°
B
G=115°
C
G=65°
D
G=57.5°

#### Slide 9 -Quizvraag

Calculating angles
Quadrilateral DEFG is a rhombus
The angle sum of a quadrilateral is 360°
A rhombus has rotation and reflection symmetry, therefore the opposite angles are equal.

D=F=115°
G=E=2(360115115)=2130=65°

#### Slide 10 -Tekstslide

Equal angles in triangle and quadrilaterals
Isosceles triangle: 2 angles (base angles) are the same size
Equilateral triangle: all 3 angles are the same size (60°)
Rhombus/Parallelogram: opposite angles are equal
Kite: 2 angles are the same size (on either side of the axis of symmetry)
Square/Rectangle: all 4 angles are the same size (90°)

#### Slide 11 -Tekstslide

Homework Tuesday
Make and correct from §11.4:
23, 24, 25, 26, 27, 28