Mathematics 5 SN
TRIGONOMETRY PROBLEMS 2
If x ,4
3 ,
3
2
, which one of the following statements is TRUE?
A)
sin x > 0 and cos x > 0
C)
sin x < 0 and cos x > 0
B)
sin x > 0 and cos x < 0
D)
sin x < 0 and cos x < 0
If ,2 < t < 2
3
, which one of the following statements is TRUE?
A)
cos t > 0 and sin t > 0
C)
cos t < 0 and sin t > 0
B)
tan t > 0 and cos t < 0
D)
sin t < 0 and tan t < 0
Given the functions f(x) = tan x and g(x) = sin x.
What are the values for which the functions f and g are 0 in [0, ]?
A)
0, 2
C)
2
, 0
B)
0,
D)
0, 2
,
1
2
3
What is the solution set of sin x 1 = 0 in ?
A)
{1}
C)
{x | x =
2 + n, n Z}
B)
2
D)
{x | x =
2 + 2n, n Z}
4
What is the solution set of the equation 2sin2x 4cos2x + 1 = 0 where x
2,
2
-?
A)
6 ,
6
-
C)
4
B)
3 ,
3
-
D)
4 ,
4
-
If x [0, 2π[, find the solution set of the following equations :
a) sin2x + cos x = 1
b) 2sin2x cos x 2 = 0
Show your work.
a)
Work
Result : The solution set is _______________.
5
6
What are the zeros in the following equation if x [0, 2]?
2sin2x 1 = 0
A)
4
- ,
4
C)
4
7 ,
4
B)
4
3 ,
4
D)
4
7 ,
4
5 ,
4
3 ,
4
Which values of x belonging to
2
3,0 satisfy the equation 4 sin3x sin x = 0?
The values of x belonging to
2
3,0 and that satisfy the equation are
_______________________________________________.
7
8
2
3Sin x in the circle with centre O, show on the
right.
Furthermore, AB // OP and m OA = 1 unit.
What is the area of the shaded region?
Show all your work.
Show all your work.
Answer: The area of the shaded region is __________ square units.
x E
A
P
B
F O
x E
A
P
B
F O
9
Find all the solutions of the equation 2cos2x 3sin x 3 = 0 such that
x
2 ,
2
3 . Give your solution in radian measure.
Show all your work.
Show all your work.
2cos2x 3sin x 3 = 0 , x
2 ,
2
3 .
Answer:
The values of x in the domain are __________________ radians.
10
What are the exact values of A that satisfy the following trigonometric equation?
sin A cot A + 2 cos2 A = 1, A [0, 2]
Show all your work.
sin A cot A + 2 cos2 A = 1, A [0, 2]
Answer:
The solution is A = __________________.
11
Given the following trigonometric equation:
2 sin2 x + 5 sin x 3 = 0, x [0, 2]
What are the exact values of x that satisfy this equation?
The exact values of x are __________ and __________.
12
Strange geometric formations, known as crop circles, have appeared in fields around the world. The creators of
the crop circle shown below would like to surround their design with a border, in the shape of an equilateral
triangle.
The circles that were used to make the design are congruent to the circle whose equation is:
x2 + y2 6x 2y 26 = 0
The circles are externally tangent to one another and tangent to the border.
What is the length of the border?
Round your answer to the nearest hundredth of a unit.
Show all your work.
13
Given the trigonometric equation:
2 cos2x + cos x = 1, x [, ]
What are the exact values of x that satisfy this equation?
The exact values of x satisfying the given equation are:
_________________________________________________.
14
A hyperbola and a trigonometric function are drawn on the same Cartesian plane. The equation of the
hyperbola is 114425
22
yx
.
F1 F2
y
x
The foci of the hyperbola are directly below two of the maxima of the trigonometric function.
Which of the following is an equation of the trigonometric function?
(Where necessary, the numbers have been rounded.)
A)
13
13cos8.28 xy
C)
11
11cos3.23 xy
B)
13
13
2cos8.28 xy
D)
11
11
2cos3.23 xy
15
Consider the equation 2 cos2 3 sin = 3
What are the solutions, in radian measure, to the equation for which 0 2?
Show all your work.
Show all your work. 0 2
2 cos2 3 sin = 3
Answer
In radian measure, the exact answers are ______________________.
16
Given the following trigonometric equation:
2 sin2x + 3 = 9 cos x, x [0, 2]
What exact values of x satisfy this equation?
The solution(s) to this equation is (are) __________________________.
Given 2 cos2 x + 3 sin x 3 = 0, x
2,0 .
What are the exact values of x?
Show all your work.
2 cos2 x + 3 sin x 3 = 0, x
2,0 .
Answer:
The exact values of x are _______________________________.
17
18
Prove the following trigonometric identity.
xx
xx cos1
cos1
sinsin
Prove the following trigonometric identity.
Show all your work.
xx
xx cos1
cos1
sinsin
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Solve the following trigonometric equation. Give the exact value(s).
2 sin2 x 3 cos x = 3 x π0,
Show all your work.
2 sin2 x 3 cos x = 3 x π0,
Answer:
The exact value(s) is (are) ___________________________ .
20
Find all solutions of 6 sin2 x 5 sin x + 1 = 0 in the interval 0, 2.
Express any inexact solutions to the nearest hundredth.
Show all your work.
6 sin2 x 5 sin x + 1 = 0
Solutions:
_______________________________________________________
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a) Work : (example)
sin2x + cos x = 1
1 cos2x + cos x = 1
cos2x cos x = 0
cos x (cos x 1) = 0
cos x = 0 or cos x = 1
2
x or
2
3 or x = 0
Result : The solution set is .2
3 ,
2 0,
b) Work : (example)
2sin2x cos x 2 = 0
2(1 cos2x) cos x 2 = 0
2 2cos2x cos x 2 = 0
2cos2x + cos x = 0
cos x (2cos x + 1) = 0
cos x = 0 or cos x = 2
1-
6
2
x or
2
3 or
3
2x or
3
4
Result : The solution set is
2
3,
3
4,
3
2,
2
D
The values of x belonging to
2
3,0 and that satisfy the equation are
,
6
5,
6,0 and
6
7.
7
8
Example of an appropriate solution
Measure of angle x
sin x = 2
3
m x = sin1
2
3
m x = 60 or m x = 3
radians
Base AB of triangle AOB
32
32ABm
Height FO of triangle AOB
2
160cosFOm
Area of triangle AOB
43.04
32
2
13Area
square units
Area of sector AOB
Area of sector AOB = (1)2
360
120 1.05 square units
Area of the shaded region 1.05 0.43 = 0.62 square units
x E
A
P
B
F O
9
Example of an appropriate solution
2cos2x 3sin x 3 = 0
2(1 sin2x) 3sin x 3 = 0
2 2sin2x 3sin x 3 = 0
-2sin2x 3sin x 1 = 0
2sin2x + 3sin x + 1 = 0
(2sin x + 1)(sin x + 1) = 0
2sin x + 1 = 0 sin x + 1 = 0
2sin x = -1 sin x = -1
sin x = 2
1-
x = 6
7,
6
11 x =
2
3
Answer The values of x in the domain are 6
11 and
2
3.
10
Example of an appropriate method
sin A cot A + 2 cos2 A = 1
sin A Asin
Acos + 2 cos2 A = 1
cos A + 2 cos2 A = 1
2 cos2 A + cos A 1 = 0
(2 cos A 1)(cos A + 1) = 0
cos A = 2
1 or cos A = -1
A = 3
or
3
5 or A =
Answer 3
, ,
3
5
The exact values of x are 6
and
6
5.
11
12
Example of an appropriate method
Equation of the circle in standard form
x2 + 6x + y2 2y = 26
(x 3)2 + (y 1)2 = 26 + 9 + 1
(x 3)2 + (y 1)2 = 36
Each radius measures 6 units
Since the three circles are congruent, the border forms an equilateral triangle.
According to the diagram on the right, A B C D
Note: Adjustments will have to be made
for different labelling.
COD is a right triangle, m OC = 6 units and m CDO = 30°
13
tan30° = CDm
OCm =
CDm
6
m CD = 10.39
m AD = m AB + m BC + m CD
= 10.39 + 12 + 10.39
32.78
Perimeter: P = 3 32.78
= 98.34
Answer: To the nearest hundredth of a unit, the border measures 98.34.
Note: Do not penalize students who did not round the answer.
Students who determined the radius of the circle have shown a partial understanding of the
problem.
The exact values of x are -, 3
,3
- ,
A
14
15
Example of an appropriate solution
01θsin1θsin2
01θsin3θsin2
3θsin3θsin22
3θsin3θsin12
3θsin3θcos2
2
2
2
2
1-θsinor2
1-θsin
For 2
1-θsin For 1-θsin
Reference angles: 6
θ
2
3θ
The sine function is negative in Quadrants III and IV.
Answer: In radian measure, the exact answers are
6
11,
2
3,
6
7θ
The exact values of x are 3
and
3
5.
16
17
Example of an appropriate solution
01sin3sin2
01sin3sin2-
03sin3sin22
03sin3sin12
03sin3cos2
2
2
2
2
2
xx
xx
xx
xx
xx
01sin1sin2 xx
2
1sin
01sin2
x
x
sin x 1 = 0
sin x = 1
Answer: The exact values of x are 6
x or
2
x .
18
Example of an appropriate proof
x
xx
xx
xx
x
xx
x
xx
xx
cos1
cos1cos1
cos1cos1
cos1cos1
cos1
cos1cos1
sin
cos1cos1
sinsin
2
2
Deduct marks if student is unable to complete the proof, but is able to arrive at x
x
cos1
cos1 2
Example of an appropriate solution
xx
xx
xx
xx
xx
xx
xx
or3
2
1cosor2
1cos
1cos1cos20
1cos3cos20
3cos3cos22
3cos3cos12
3cos3sin2
2
2
2
2
Answer: The exact values are πor3
2π xx .
19
20
Students who were able to arrive at 0 = (2 cos x + 1) (cos x + 1) have shown they have a partial understanding of the problem.
Example of an appropriate solution
80.2,6
5,
6,34.0
6
5
680.234.0
2
1sin
3
1sin
01sin201sin3
01sin21sin3
01sin5sin6 2
x
xx
xx
xx
xx
xx
oror
Note: Students who used an appropriate method to determine two of the four answers have shown they
have a partial understanding of the problem.
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