2Tvwo § 4.3 Similar figures

• Wiskunde
• Middelbare school
• vwo
• Leerjaar 2

§ 4.3 Similar figures

This lesson:

a. explanation exercise 16

b. new THEORY, about § 4.3

c. more new THEORY, about § 4.3

d. explanation of an exercise from § 4.2?

e. do § 4.3

WHY studying 16 together now?

Because it is the last exercise of the paragraph and, as usual, 

it is a little more difficult than the others.

I noticed that not everybody put in enough effort to crack this one!

Now we do this one together. In future work out all the exercises seriously.

Look in your textbook, page 132.

In the next slide you see how exercise 16 could be solved.

Explanation exercise 16:

16 a) The scale factor used to enlarge the height of the photo to the height of the 

screen is 1080 : 1000 = 1.08. 

b) The width of the photo on the screen becomes 1600 x 1.08 = 1728 pixels. 

That strip is 1920 – 1728 = 192 pixels wide. 

c) The scale factor used to enlarge the width of the photo to the width of the 

screen is 1920 : 1600 = 1.2. The height of the photo on the screen would then be 1000 x 1.2 = 1200 pixels. In that case, 1200 - 1080 = 120 pixels would not fit in the height of the screen. 

Theory, part 1.

What to do, to prove SIMILARITY of 2 figures ?!

• work on the ANGLES, and
• work on the SIDES
• both are needed, to prove SIMILARITY !
• the next slide explains this more
• because nothing beats an example!

Theory, part 2.

When to practise this?

In exercises 20 and 21 this Method is needed.

So, you have to work on both:

• angles, and
• sides
• only then Similarity (or not) is proved!

Start doing the Homework.

Time for a Joke?

Ask your teacher!

Any questions?

Go on with § 4.3

Make sure you do not have much Homework!