2Tvwo §8.3 Trapezium

• Wiskunde
• Middelbare school
• havo, vwo
• Leerjaar 2

§8.3 Trapezium

Learning goals:   

1. what is a trapezium?

2. how to calculate the area of a trapezium?

We are going to do this Task right now. So:

1. Open your Notebook and

2. take a pen(cil) from your pencil case

Make this task in your Notebook.

SOLUTION:

Make 17b in your Notebook now.

SOLUTION:

Make 17c in your Notebook now.

SOLUTION 17c:

Let's look at 17b once more. Here the Area of the 

Parallelogram is calculated as the SUM of the Areas of the two Triangles:

QUESTION:

Isn't it possible to do this quicker, 

as follows:

Area PQRS = 1/2 x 4 x (9 + 10) ?! Check this.

Answer in the next slide!

Is it possible?

1. yes
2. no
3. it depends

 Areas of the two Triangles:

Yes it is possible to do this quicker!

as follows:

Area PQRS = 1/2 x 4 x (9 + 10) = 1/2 x 4 x 19 = 38

This result is the same as you see above:

Area PQRS = 18 + 20 = 38

Next slide summarizes this in a Theory.

From now on we will not divide up the Trapezium in two Triangles any more.

So the picture on the right will be used in the exercises.

What is an ISOSCELES triangle?

1. a right-angled triangle
2. a triangle with 3 equal sides and angles
3. a triangle with 2 equal sides and angles
4. an obtuse angled triangle

Which is the colour of the ISOSCELES triangle?

What colour does the ISOSCELES
triangle have?

1. green
2. blue
3. pink
4. purple

The ISOSCELES triangle is the PINK one!

It has two equal sides. This is important in exercise 20.

To be more precise, also

the purple triangle is an isosceles one.

Two equal sides and angles is enough

for this, but all three being equal

 is also fine!

Homework:

Make the following tasks:

-  19, 20, 21. and make a choice between:

    S19.   or one of these: C5 or C6

Later a little more information is given in this Lesson Up!

When I see this exercise, it gets dark before my eyes...

All this information is ABACADABRA to me.

What is THE WAY to go from darkness to light?

Think about this.

SOLUTION:

Making a SKETCH will help you out!! Look:

The last TIP:

Sometimes you can't get around

using the THEOREM of PYTHAGORAS!

Like here, because you need to know

the height of the parallelogram!

Homework:

Make the following tasks:

-  19, 20, 21. and make a choice between:

    S19.   or one of these: C5 or C6

Later a little more information is given in this Lesson Up!