# Trigonometry - PowerPoint PPT Presentation

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## Trigonometry

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### Trigonometry What is trigonometry? It only works for right angle triangles It is useful in building and surveying to work out the height of buildings It is used by ... – PowerPoint PPT presentation

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Title: Trigonometry

1
Trigonometry
2
What is trigonometry?
• It only works for right angle triangles
• It is useful in building and surveying to work
out the height of buildings
• It is used by aeroplanes and space shuttles
landing to make sure they do not crash

3
How does it work?
• First you need to be able to label the parts of a
triangle
• The easiest is the longest side, the hypotenuse
• Where is it?

Hypotenuse (it is always opposite the right angle)
4
Labelling the sides
• You need to identify which angle (not the right
angle) we know
• There are two other sides
• The opposite is the side opposite the angle,
where is it?
• The adjacent is the other side, beside it. Where
is it?

Hypotenuse
Opposite
5
SOHCAHTOA
• These are the equations you need to use to work
out the angle
• They are
• SO/H
• Sin Opposite/Hypotenuse
• C A/H
• TO/A

6
Working Out One Side
• If you want to find an unknown side you first
have to work out which part of SOHCAHTOA you are
going to use
• E.g.

We know the hypotenuse and we need to find the
opposite side (x) Which equation do we use? Sin
O/H Sin is a button on the calculator Sin72
X/10 0.95 x/10 9.5m x (this is smaller than
the hypotenuse)
10m
x
72
7
Try these
15cm
w
x
53
72
8cm
49
z
12cm
y
65
12cm
8
• X 14.3cm
• Y 5.1cm
• W 10.6cm
• Z 9.1cm

9
Finding An Angle
• To find an angle you divide the two sides you
know and press shift sin/cos/tan
• E.g.

We want to find out what angle a is? Which
equation do we use? Cos A/H Cos a 5/10 Cos a
0.5 A 60
10cm
a
5cm
10
Try these
F
7cm
25cm
15cm
8cm
G
5cm
9cm
10cm
6cm
H
I
11