# 2Tvwo §6.5 Right, acute or obtuse

§6.3 Right, acute or obtuse ?
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WiskundeMiddelbare schoolvwoLeerjaar 2

This lesson contains 35 slides, with interactive quizzes and text slides. Lesson duration is: 50 min

## Items in this lesson

§6.3 Right, acute or obtuse ?

#### Slide 1 -Slide

Before going over to §6.5...
Let's Study the last exercise from §6.4!

#### Slide 2 -Slide

+ Check if you have exercise 30

#### Slide 3 -Slide

If you do have 30, then

be proud and   stand up!

exercise 30

#### Slide 5 -Slide

What makes this exercise difficult, is...
that you do not have a 3D picture of the pyramid!
This makes it hard to imagine what all the information in words means.
'Use cross-section LTN .......'  - What's all that??!

#### Slide 6 -Slide

Question:
What could you do first, to solve this problem?
(How to have a good overview on all information?)

#### Slide 9 -Slide

Make my own 3D sketch of the pyramid!

#### Slide 10 -Slide

Here is my sketch.
Indeed, a true
work of Art!

#### Slide 11 -Slide

Once more the exercise and the 3D pic:

#### Slide 12 -Slide

Now only we sketch cross-section LTN !
Then we take a few steps:
1st  In LTN we draw a help-line: TX. This is the height we have to calculate.
2nd  We calculate LN  (in order to know NX !).
3rd  We calculate NX.
4th We calculate height TX !

#### Slide 14 -Slide

§6.5 at last...
Some new words:
+  converse (The converse Pythagoras' theorem; in between 31 and 32)
= opposite (omgekeerde)
+  Two slats of wood are fixed together by a hinge. (33)
hinge =  scharnier

#### Slide 15 -Slide

Write the solutions in your Notebook!
It is an important
exercise to understand this paragraph.

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Solution:

#### Slide 19 -Slide

Copy the SCHEME, fill it in
and calculate BC.
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Solution:

#### Slide 21 -Slide

Also EXPLAIN why (not)!
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Solution:

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Solution:

#### Slide 25 -Slide

This is what we've learnt now:

#### Slide 27 -Slide

Homework time.
Later on a few more slides follow.

#### Slide 28 -Slide

Question: If the text below is the 'converse Pythagoras' Theorem, then what is the 'original one'?!  Answer on next slide.

#### Slide 29 -Slide

Answer: the original theorem you see below (p.201).
In the converse one we draw the CONCLUSION that the triangle is right-angled!

#### Slide 30 -Slide

how to know which side is the longest, 24 or                   ?
(Important, because that one has to below, in the Scheme!)
600

#### Slide 31 -Slide

[?]600
How to find which is greatest:
or 24 ?!

#### Slide 32 -Mind map

LM =                     is the longest,
because KL = 24 and KM = 2.
600
600
600

#### Slide 33 -Slide

Tip for 33:
This exercise is a GREAT INTRODUCTION + EXPLANATION
for the rest of the whole paragraph!
Make sure you understand this one, before you go on!

#### Slide 34 -Slide

Homework time again!