# 3Tvwo §6.4 / 3Thavo §6.5 Calculating in right-angled triangles.

§6.4 / §6.5 Calculating in right-angled triangles
Choose the right Formula-in-letters, that tells you how to calculate the
SINE,   COSINE  and  TANGENT, in the next slide.
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Slide 1: Slide
WiskundeMiddelbare schoolhavo, vwoLeerjaar 3

This lesson contains 21 slides, with interactive quizzes and text slides.

Lesson duration is: 50 min

## Items in this lesson

§6.4 / §6.5 Calculating in right-angled triangles
Choose the right Formula-in-letters, that tells you how to calculate the
SINE,   COSINE  and  TANGENT, in the next slide.

#### Slide 1 -Slide

vwo §6.4 / havo §6.5
Calculating in right-angled triangles
Because it's been a while since you worked on this Chapter -holiday!- we will look back shortly on the
content you learned up to now!

VWO classes:   STUDY SQUARERS, feel free to go to the STUDY SQUARE, doing § 6.4 on your own.

#### Slide 2 -Slide

The correct letterformula is:
A
SAH COA TAH
B
SIN COS TOA
C
COH TAH SIN
D
SOH CAH TOA

#### Slide 3 -Quiz

meaning:
Sine = Opposite shorter side / Hypotenuse
Cosine = Adjacent shorter side / Hypotenuse
Tangent = Opposite shorter side / Adjacent shorter side

#### Slide 5 -Slide

§6.4/§6.5 Calculating in right-angled triangles
You now know the:
+  sine, cosine and tangent
+ but when do you use which of these?
+ that is shown in the next slides!
+ FIRST WE DO 21 TOGETHER!

#### Slide 9 -Slide

Homework time.
+    Do §6.4 vwo / §6.5 havo Calculating in right-angled triangles
+    Later a new technique will be explained, that you need to do         the last 3 exercises!

#### Slide 10 -Slide

Explanation for the last 3 exercises of the paragraph.

#### Slide 11 -Slide

If you want to calculate length PQ,
then              what is the problem?

#### Slide 12 -Slide

What's the pro, bro (sis)?
So: describe the problem!

#### Slide 13 -Mind map

The big problem is:
there is no right angle to be seen?!
Pythagoras only works in right-angled triangles!
The method to solve this problem is shown in the next slide.

#### Slide 16 -Slide

Now there are even two right-angled triangles!
REMEMBER: WE ARE AFTER: length PQ!!
1. draw auxiliary line (=helplijn) RS.
2. calculate RS with sine angle P
3. calculate PS with cosine angle P (or tangent angle P)
4. calculate QS with tangent angle Q
5. add PS to QS to get length PQ

#### Slide 17 -Slide

helping line = auxiliary line

#### Slide 18 -Slide

Homework time again.
In the next slide an Oldie-but-Goldie...