Transcript Chapter 14 - Drawing Triangles

Drawing Triangles
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MTH 3.16a
1.
Using a Protractor
2.
Select SAS triangles
3.
Select ASA triangles
4.
Select SSS triangles
16-Jul-15
Created by Mr. Lafferty
1
(SAS) Starter Questions
Q1.
Convert the percentages to fractions.
(a)
Q2.
30%
(b)
60%
Write down all the factors of 16.
80
Q3.
Calculate the missing angles.
Q4.
Round the following to 1 decimal place.
(a)
16-Jul-15
4.549
(b)
o
6.551
Created by Mr. Lafferty
2
A 180o Protractor
Outside scale from
0o to 180o going in a
clockwise direction.
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Inside scale from
0o to 180o going in an
anti-clockwise direction.
3
You need to be able to measure an angle to the nearest
degree. To help you do this you should always:
1. Look directly down onto the cross point.
2. Always use the protractor in a horizontal manner as shown
below.

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4
1
Measuring
Angles with a
180o Protractor
50o
2
0 on the inside so
use inside scale
67o
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0 on the outside so
use outside scale
5
3
Measuring
Angles with a
180o Protractor
120o
4
135o
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0 on the outside so
use outside scale
0 on the inside so
use inside scale
6
Drawing SAS Triangles
Aim of the Lesson
‘We are learning to construct a triangle given
the length of two sides
and the included angle’
16-Jul-15
Created by Mr. Lafferty
7
Drawing SAS Triangles
SAS Triangles
Side
Angle
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Side
Created by Mr. Lafferty
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Drawing SAS Triangles
Toolkit required
1.Ruler
2.Protractor
3.Pencil & Paper
16-Jul-15
Created by Mr. Lafferty
9
Drawing SAS Triangles
C
Example :
30
o
B
A
Draw to scale the triangle ABC
with AB = 6cm and angle CAB = 30o and AC = 5cm
Step 1 Draw line AB=6cm
Step 2 Measure
angle CAB
from A
C
X
Step 3 Draw the line
AC = 5cm
through X. Label it C.
A
B
Step 4 Join C to B.
Check angles add to 180o
16-Jul-15
Created by Mr. Lafferty
10
Drawing SAS Triangles
Some practice
Teejay Book
Page 169 Exercise 1
16-Jul-15
Created by Mr. Lafferty
11
(ASA) Starter Questions
Q1.
Convert to the 24 hour clock.
(a)
7:25 pm (b)
6:50 am
Q2.
Write down lowest common multiple of 3, 4 , 5.
Q3.
List the first 4 prime numbers.
Q4.
Round the following to nearest 1000.
(a)
16-Jul-15
12,501
(b)
369,765
Created by Mr. Lafferty
12
Drawing SAS Triangles
Part 2 : ASA triangles
16-Jul-15
Created by Mr. Lafferty
13
Drawing ASA Triangles
Aim of the Lesson
‘‘We are learning to construct a triangle given
two angles
and the length of the side in between’.
16-Jul-15
Created by Mr. Lafferty
14
Drawing ASA Triangles
ASA Triangles
Angle
Side
16-Jul-15
Angle
Created by Mr. Lafferty
15
Drawing ASA Triangles
Toolkit required
1.Ruler
2.Protractor
3.Pencil & Paper
16-Jul-15
Created by Mr. Lafferty
16
Drawing ASA Triangles
R
Example :
Q
P
Draw to scale the triangle PQR
with PQ = 8cm and angle RPQ = 30o and RQP = 40o
Step 1 Draw line PQ
Step 2 Measure
Angle RPQ
from P
R
Step 3 Measure
angle RQP
from Q
Q
P
Step 4 Intersection point is R
Check angles add to 180o
16-Jul-15
Created by Mr. Lafferty
17
Drawing ASA Triangles
Some practice
Teejay Book
Page 171 Exercise 2
16-Jul-15
Created by Mr. Lafferty
18
(SSS) Starter Questions
Q1.
Convert to the 12 hour clock.
(a)
17:15
(b)
05:40
Q2.
Write down lowest common multiple of 3, 4 , 5.
Q3.
List the prime numbers between 10 and 20.
Q4.
Round the following to nearest 100.
(a)
16-Jul-15
13,551
(b)
369,449
Created by Mr. Lafferty
19
Drawing SSS Triangles
Part 3 : SSS triangles
16-Jul-15
Created by Mr. Lafferty
20
Drawing SSS Triangles
Aim of the Lesson
‘‘We are learning to construct a triangle given
the length of three sides’.
16-Jul-15
Created by Mr. Lafferty
21
Drawing SSS Triangles
SSS Triangles
Side
Side
16-Jul-15
Side
Created by Mr. Lafferty
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Drawing SSS Triangles
Toolkit required
1.Ruler
2.Compass
3.Pencil & Paper
16-Jul-15
Created by Mr. Lafferty
23
Drawing SSS Triangles
Z
Example :
X
Draw to scale the triangle XYZ
with XY = 3cm and XZ = 5cm and YZ = 4cm
Step 1 Draw line XY=3cm
y
Z
Step 2 Use your compass to draw part of
a circle centre X radius XZ=5cm
Step 3 Use your compass to draw part of
a circle centre Y radius YZ=4cm
Step 4 Intersection point is labelled Z
X
Y
Step 5 Draw in line XZ and YZ to complete triangle
Check angles add to 180o
16-Jul-15
Created by Mr. Lafferty
24
Drawing SSS Triangles
Some practice
Teejay Book
Page 173 Exercise 3
16-Jul-15
Created by Mr. Lafferty
25