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Unit 1:
Negative Numbers
UNIT 8
TRIGONOMETRY
B a s i c E s s e n t i a l
A d d i t i o n a l M a t h e m a t i c s S k i l l s
Curriculum Development Division
Ministry of Education Malaysia
TABLE OF CONTENTS
Module Overview 1
Part A: Trigonometry I 2
Part B: Trigonometry II 6
Part C: Trigonometry III 11
Part D: Trigonometry IV 15
Part E: Trigonometry V 19
Part F: Trigonometry VI 21
Part G: Trigonometry VII 25
Part H: Trigonometry VIII 29
Answers 33
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
1 Curriculum Development Division
Ministry of Education Malaysia
MODULE OVERVIEW
1. The aim of this module is to reinforce pupils’ understanding of the concept
of trigonometry and to provide pupils with a solid foundation for the study
of trigonometric functions.
2. This module is to be used as a guide for teacher on how to help pupils to
master the basic skills required for this topic. Part of the module can be
used as a supplement or handout in the teaching and learning involving
trigonometric functions.
3. This module consists of eight parts and each part deals with one specific
skills. This format provides the teacher with the freedom of choosing any
parts that is relevant to the skills to be reinforced.
4. Note that Part A to D covers the Form Three syllabus whereas Part E to H
covers the Form Four syllabus.
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
2 Curriculum Development Division
Ministry of Education Malaysia
TEACHING AND LEARNING STRATEGIES
Some pupils may face difficulties in remembering the definition and
how to identify the correct sides of a right-angled triangle in order to
find the ratio of a trigonometric function.
Strategy:
Teacher should make sure that pupils can identify the side opposite to
the angle, the side adjacent to the angle and the hypotenuse side
through diagrams and drilling.
PART A:
TRIGONOMETRY I
LEARNING OBJECTIVE
Upon completion of Part A, pupils will be able to identify opposite,
adjacent and hypotenuse sides of a right-angled triangle with reference
to a given angle.
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
3 Curriculum Development Division
Ministry of Education Malaysia
Opposite side is the side opposite or facing the angle .
Adjacent side is the side next to the angle .
Hypotenuse side is the side facing the right angle and is the longest side.
LESSON NOTES
θ
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
4 Curriculum Development Division
Ministry of Education Malaysia
Example 1:
AB is the side facing the angle , thus AB is the opposite side.
BC is the side next to the angle , thus BC is the adjacent side.
AC is the side facing the right angle and it is the longest side, thus AC is the
hypotenuse side.
Example 2:
QR is the side facing the angle , thus QR is the opposite side.
PQ is the side next to the angle , thus PQ is the adjacent side.
PR is the side facing the right angle or is the longest side, thus PR is the
hypotenuse side.
EXAMPLES
θ
θ
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
5 Curriculum Development Division
Ministry of Education Malaysia
Identify the opposite, adjacent and hypotenuse sides of the following right-angled triangles.
1.
Opposite side =
Adjacent side =
Hypotenuse side =
2.
Opposite side =
Adjacent side =
Hypotenuse side =
3.
Opposite side =
Adjacent side =
Hypotenuse side =
4.
Opposite side =
Adjacent side =
Hypotenuse side =
5.
Opposite side =
Adjacent side =
Hypotenuse side =
6.
Opposite side =
Adjacent side =
Hypotenuse side =
TEST YOURSELF A
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
6 Curriculum Development Division
Ministry of Education Malaysia
PART B:
TRIGONOMETRY II
TEACHING AND LEARNING STRATEGIES
Some pupils may face problem in
(i) defining trigonometric functions; and
(ii) writing the trigonometric ratios from a given right-angled
triangle.
Strategy:
Teacher must reinforce the definition of the trigonometric functions
through diagrams and examples. Acronyms SOH, CAH and TOA can
be used in defining the trigonometric ratios.
LEARNING OBJECTIVE
Upon completion of Part B, pupils will be able to state the definition
of the trigonometric functions and use it to write the trigonometric
ratio from a right-angled triangle.
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
7 Curriculum Development Division
Ministry of Education Malaysia
Definition of the Three Trigonometric Functions
(i) sin = opposite side
hypotenuse side
(ii) cos = adjacent side
hypotenuse side
(iii) tan = opposite side
adjacent side
sin = opposite side
hypotenuse side
= AB
AC
cos = adjacent side
hypotenuse side =
BC
AC
tan = opposite side
adjacent side=
AB
BC
LESSON NOTES
Acronym:
SOH:
Sine – Opposite - Hypotenuse
Acronym:
CAH:
Cosine – Adjacent - Hypotenuse
Acronym:
TOA:
Tangent – Opposite - Adjacent
θ
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
8 Curriculum Development Division
Ministry of Education Malaysia
Example 1:
AB is the side facing the angle , thus AB is the opposite side.
BC is the side next to the angle , thus BC is the adjacent side.
AC is the side facing the right angle and is the longest side, thus AC is the hypotenuse
side.
Thus sin = opposite side
hypotenuse side =
AB
AC
cos = adjacent side
hypotenuse side =
BC
AC
tan = opposite side
adjacent side =
AB
BC
EXAMPLES
θ
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
9 Curriculum Development Division
Ministry of Education Malaysia
Example 2:
WU is the side facing the angle, thus WU is the opposite side.
TU is the side next to the angle, thus TU is the adjacent side.
TW is the side facing the right angle and is the longest side, thus TW is the hypotenuse
side.
Thus, sin = opposite side
hypotenuse side =
WU
TW
cos = adjacent side
hypotenuse side =
TU
TW
tan = opposite side
adjacent side =
WU
TU
You have to identify the
opposite, adjacent and
hypotenuse sides.
θ
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
10 Curriculum Development Division
Ministry of Education Malaysia
Write the ratios of the trigonometric functions, sin , cos and tan , for each of the diagrams
below:
1.
sin =
cos =
tan =
2.
sin =
cos =
tan =
3.
sin =
cos =
tan =
4.
sin =
cos =
tan =
5.
sin =
cos =
tan =
6.
sin =
cos =
tan =
TEST YOURSELF B
θ
θ
θ
θ
θ
θ
θ
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
11 Curriculum Development Division
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PART C:
TRIGONOMETRY III
TEACHING AND LEARNING STRATEGIES
Some pupils may face problem in finding the angle when given
two sides of a right-angled triangle and they also lack skills in
using calculator to find the angle.
Strategy:
1. Teacher should train pupils to use the definition of each
trigonometric ratio to write out the correct ratio of the sides
of the right-angle triangle.
2. Teacher should train pupils to use the inverse trigonometric
functions to find the angles and express the angles in degree
and minute.
LEARNING OBJECTIVE
Upon completion of Part C, pupils will be able to find the angle of
a right-angled triangle given the length of any two sides.
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
12 Curriculum Development Division
Ministry of Education Malaysia
Find the angle in degrees and minutes.
Example 1:
sin = 2
5
o
h
= sin-1
2
5
= 23o 34 4l
= 23o 35
(Note that 34 41 is rounded off to 35)
Example 2:
cos = a
h =
3
5
= cos-1
3
5
= 53o 7 48
= 53o 8
(Note that 7 48 is rounded off to 8)
Since sin = opposite
hypotenuse
then = sin-1
opposite
hypotenuse
Since cos = adjacent
hypotenuse
then = cos-1 adjacent
hypotenuse
Since tan = opposite
adjacent
then = tan-1
opposite
adjacent
1 degree = 60 minutes 1 minute = 60 seconds
1o = 60 1 = 60
Use the key D M S or on your calculator to express the angle in degree and minute.
Note that the calculator expresses the angle in degree, minute and second. The angle in
second has to be rounded off. ( 30, add 1 minute and < 30, cancel off.)
LESSON NOTES
EXAMPLES
θ
θ
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
13 Curriculum Development Division
Ministry of Education Malaysia
Example 3:
tan = o
a =
7
6
= tan-1
7
6
= 49o 23 55
= 49o 24
Example 4:
cos = a
h =
5
7
= cos-1
5
7
= 44o 24 55
= 44o 25
Example 5:
sin = o
h =
4
7
= sin-1
4
7
= 34o 50 59
= 34o 51
Example 6:
tan = o
a =
5
6
= tan-1
5
6
= 39o 48 20
= 39o 48
θ
θ
θ
θ
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
14 Curriculum Development Division
Ministry of Education Malaysia
Find the value of in degrees and minutes.
1.
2.
3.
4.
5.
6.
TEST YOURSELF C
θ θ
θ
θ
θ
θ
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
15 Curriculum Development Division
Ministry of Education Malaysia
PART D:
TRIGONOMETRY IV
TEACHING AND LEARNING STRATEGIES
Pupils may face problem in finding the length of the side of a
right-angled triangle given one angle and any other side.
Strategy:
By referring to the sides given, choose the correct trigonometric
ratio to write the relation between the sides.
1. Find the length of the unknown side with the aid of a
calculator.
LEARNING OBJECTIVE
Upon completion of Part D, pupils will be able to find the
angle of a right-angled triangle given the length of any two
sides.
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
16 Curriculum Development Division
Ministry of Education Malaysia
Find the length of PR.
With reference to the given angle, PR is the
opposite side and QR is the adjacent side.
Thus tangent ratio is used to form the
relation of the sides.
tan 50o =
5
PR
PR = 5 tan 50o
Find the length of TS.
With reference to the given angle, TR is the
adjacent side and TS is the hypotenuse
side.
Thus cosine ratio is used to form the
relation of the sides.
cos 32o =
8
TS
TS cos 32o = 8
TS = 8
cos32o
LESSON NOTES
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
17 Curriculum Development Division
Ministry of Education Malaysia
Find the value of x in each of the following.
Example 1:
tan 25o =
3
x
x = 3
tan 25o
= 6.434 cm
Example 2:
sin 41.27o =
5
x
x = 5 sin 41.27o
= 3.298 cm
Example 3:
cos 34o 12 =
6
x
x = 6 cos 34o 12
= 4.962 cm
Example 4:
tan 63o =
9
x
x = 9 tan 63o
= 17.66 cm
EXAMPLES
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
18 Curriculum Development Division
Ministry of Education Malaysia
Find the value of x for each of the following.
1.
2.
3.
4.
5.
6.
TEST YOURSELF D
10 cm
6 cm
13 cm
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
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PART E:
TRIGONOMETRY V
TEACHING AND LEARNING STRATEGIES
Pupils may face problem in relating the coordinates of a given
point to the definition of the trigonometric functions.
Strategy:
Teacher should use the Cartesian plane to relate the coordinates
of a point to the opposite side, adjacent side and the hypotenuse
side of a right-angled triangle.
LEARNING OBJECTIVE
Upon completion of Part E, pupils will be able to state the
definition of trigonometric functions in terms of the
coordinates of a given point on the Cartesian plane and use
the coordinates of the given point to determine the ratio of the
trigonometric functions.
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
20 Curriculum Development Division
Ministry of Education Malaysia
In the diagram, with reference to the angle , PR is the opposite side, OP is the adjacent side
and OR is the hypotenuse side.
r
y
OR
PR
hypotenuse
oppositesin
r
x
OR
OP
hypotenuse
adjacentcos
x
y
OP
PR
adjacent
oppositetan
LESSON NOTES
θ
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
21 Curriculum Development Division
Ministry of Education Malaysia
PART F:
TRIGONOMETRY VI
TEACHING AND LEARNING STRATEGIES
Pupils may face difficulties in determining that the sign of the x-coordinate
and y-coordinate affect the sign of the trigonometric functions.
Strategy:
Teacher should use the Cartesian plane and use the points on the four
quadrants and the values of the x-coordinate and y-coordinate to show how the
sign of the trigonometric ratio is affected by the signs of the x-coordinate and
y-coordinate.
Based on the A – S – T – C, the teacher should guide the pupils to determine
on which quadrant the angle is when given the sign of the trigonometric ratio
is given.
(a) For sin to be positive, the angle must be in the first or second
quadrant.
(b) For cos to be positive, the angle must be in the first or fourth
quadrant.
(c) For tan to be positive, the angle must be in the first or third quadrant.
LEARNING OBJECTIVE
Upon completion of Part F, pupils will be able to relate the sign of the
trigonometric functions to the sign of x-coordinate and y-coordinate and to
determine the sign of each trigonometric ratio in each of the four quadrants.
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
22 Curriculum Development Division
Ministry of Education Malaysia
First Quadrant
sin = y
r (Positive)
cos = x
r(Positive)
tan = y
x(Positive)
(All trigonometric ratios are positive in the
first quadrant)
Second Quadrant
sin = y
r (Positive)
cos = x
r
(Negative)
tan = y
x(Negative)
(Only sine is positive in the second
quadrant)
Third Quadrant
sin = y
r
(Negative)
cos = x
r
(Negative)
tan = y y
x x
(Positive)
(Only tangent is positive in the third
quadrant)
Fourth Quadrant
sin = y
r
(Negative)
cos = x
r (Positive)
tan = y
x
(Negative)
(Only cosine is positive in the fourth
quadrant)
LESSON NOTES
θ θ
θ θ
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
23 Curriculum Development Division
Ministry of Education Malaysia
Using acronym: Add Sugar To Coffee (ASTC)
sin is positive
sin is negative
cos is positive
cos is negative
tan is positive
tan is negative
A – All positive
C – only cos is positive T – only tan is positive
S – only sin is positive
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
24 Curriculum Development Division
Ministry of Education Malaysia
State the quadrants the angle is situated and show the position using a sketch.
1. sin = 0.5
2. tan = 1.2
3. cos = −0.16
4. cos = 0.32
5. sin = −0.26 6. tan = −0.362
TEST YOURSELF F
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
25 Curriculum Development Division
Ministry of Education Malaysia
PART G:
TRIGONOMETRY VII
TEACHING AND LEARNING STRATEGIES
Pupils may face problem in calculating the length of the sides of a
right-angled triangle drawn on a Cartesian plane and determining the
value of the trigonometric ratios when a point on the Cartesian plane is
given.
Strategy:
Teacher should revise the Pythagoras Theorem and help pupils to
recall the right-angled triangles commonly used, known as the
Pythagorean Triples.
LEARNING OBJECTIVE
Upon completion of Part G, pupils will be able to calculate the length
of the side of right-angled triangle on a Cartesian plane and write the
value of the trigonometric ratios given a point on the Cartesian plane
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
26 Curriculum Development Division
Ministry of Education Malaysia
The Pythagoras Theorem:
(a) 3, 4, 5 or equivalent (b) 5, 12, 13 or equivalent (c) 8, 15, 17 or equivalent
The sum of the squares of two sides of
a right-angled triangle is equal to the
square of the hypotenuse side.
PR2 + QR
2 = PQ
2
LESSON NOTES
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
27 Curriculum Development Division
Ministry of Education Malaysia
1. Write the values of sin , cos and tan
from the diagram below.
OA2 = (−6)
2 + 8
2
= 100
OA = 100
= 10
sin = 8 4
10 5
y
r
cos = 6 3
10 5
x
r
tan = 8 4
6 3
y
x
2. Write the values of sin , cos and tan
from the diagram below.
OB2 = (−12)
2 + (−5)
2
= 144 + 25
= 169
OB = 169
= 13
sin = 5
13
y
r
cos = 12
13
x
r
tan = 5 5
12 12
EXAMPLES
θ θ
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
28 Curriculum Development Division
Ministry of Education Malaysia
Write the value of the trigonometric ratios from the diagrams below.
1.
sin =
cos =
tan =
2.
sin =
cos =
tan =
3.
sin =
cos =
tan =
4.
sin =
cos =
tan =
5.
sin =
cos =
tan =
6.
sin =
cos =
tan =
TEST YOURSELF G
θ θ θ
θ
θ
θ θ
B(5,4)
B(5,12)
x
y
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
29 Curriculum Development Division
Ministry of Education Malaysia
PART H:
TRIGONOMETRY VIII
TEACHING AND LEARNING STRATEGIES
Pupils may find difficulties in remembering the shape of the
trigonometric function graphs and the important features of the
graphs.
Strategy:
Teacher should help pupils to recall the trigonometric graphs which
pupils learned in Form 4. Geometer’s Sketchpad can be used to
explore the graphs of the trigonometric functions.
LEARNING OBJECTIVE
Upon completion of Part H, pupils will be able to sketch the
trigonometric function graphs and know the important features of the
graphs.
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
30 Curriculum Development Division
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(a) y = sin x
The domain for x can be from 0o to 360
o or 0 to 2 in radians.
Important points: (0, 0), (90o, 1), (180
o, 0), (270
o, −1) and (360
o, 0)
Important features: Maximum point (90o, 1), Maximum value = 1
Minimum point (270o, −1), Minimum value = −1
(b) y = cos x
Important points:(0o, 1), (90
o, 0), (180
o, −1), (270
o, 0) and (360
o, 1)
Important features: Maximum point (0o, 1) and (360
o, 1),
Maximum value = 1 Minimum point (180o, −1)
Minimum value = 1
LESSON NOTES
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
31 Curriculum Development Division
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(c) y = tan x
Important points: (0o, 0), (180
o, 0) and (360
o, 0)
Is there any
maximum or
minimum point
for the tangent
graph?
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
32 Curriculum Development Division
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1. Write the following trigonometric functions to the graphs below:
y = cos x y = sin x y = tan x
2. Write the coordinates of the points below:
(a)
(b)
A(0,1)
TEST YOURSELF H
y = cos x y = sin x
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
33 Curriculum Development Division
Ministry of Education Malaysia
TEST YOURSELF A:
1. Opposite side = AB
Adjacent side = AC
Hypotenuse side = BC
2. Opposite side = PQ
Adjacent side = QR
Hypotenuse side = PR
3. Opposite side = YZ
Adjacent side = XZ
Hypotenuse side = XY
4. Opposite side = LN
Adjacent side = MN
Hypotenuse side = LM
5. Opposite side = UV
Adjacent side = TU
Hypotenuse side = TV
6. Opposite side = RT
Adjacent side = ST
Hypotenuse side = RS
TEST YOURSELF B:
1. sin = AB
BC
cos = AC
BC
tan = AB
AC
2. sin = PQ
PR
cos = QR
PR
tan = PQ
QR
3. sin = YZ
YX
cos = XZ
XY
tan = YZ
XZ
4. sin = LN
LM
cos = MN
LM
tan = LN
MN
5. sin = UV
TV
cos = UT
TV
tan = UV
UT
6. sin = RT
RS
cos = ST
RS
tan = RT
TS
ANSWERS
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
34 Curriculum Development Division
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TEST YOURSELF C:
1. sin = 1
3
= sin-1
1
3 = 19
o 28
2. cos = 1
2
= cos-1
1
2 = 60
o
3. tan = 5
3
= tan-1
5
3 = 59
o 2
4. cos = 5
8
= cos-1
5
8 = 51
o 19
5. tan = 7.5
9.2
= tan-1
7.5
9.2 = 39
o 11
6. sin = 6.5
8.4
= sin-1
6.5
8.4= 50
o 42
TEST YOURSELF D:
1. tan 32o =
4
x
x = 4
tan 32o = 6.401 cm
2. sin 53.17o =
7
x
x = 7 sin 53.17o = 5.603 cm
3. cos 74o 25 =
10
x
x = 10 cos 74o 25
= 2.686 cm
4. sin 551
3
o
= 6
x
x = 13
6
sin55o
= 7.295 cm
5. tan 47o =
13
x
x = 13 tan 47o = 13.94 cm
6. cos 61o =
10
x
x = 10
cos61o= 20.63 cm
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
35 Curriculum Development Division
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TEST YOURSELF F:
1. 1ST
and 2nd
2. 1st and 3
rd
3. 2nd
and 3rd
4. 1st and 4
th
5. 3rd
and 4th
6. 2nd
and 4th
TEST YOURSELF G:
1. sin = 4
5
cos = 3
5
tan = 4
3
2. sin = 12
13
cos = 5
13
tan = 12
5
3. sin = 4
5
cos = 3
5
tan = 4
3
4. sin = 4
5
cos = 3
5
tan = 4
3
5. sin = 8
17
cos = 15
17
tan = 8
15
6. sin = 5
13
cos = 12
13
tan = 5
12
Basic Essentials Additional Mathematics Skills (BEAMS) Module
Unit 8: Trigonometry
36 Curriculum Development Division
Ministry of Education Malaysia
TEST YOURSELF H:
1.
y = tan x y = sin x y = cos x
2. (a) A (0, 1), B (90o, 0), C (180
o, 1), D (270
o, 0)
(b) P (90o, 1), Q (180
o, 0), R (270
o, 1), S (360
o, 0)