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Mathematics
WAEC / WASSCE 2019
Geometry and Trigonometry
Solution
An arc subtends an angle of 72\(^o\) at the centre of a circle. Find the length of the arc if the radius of the circle is 3.5 cm. [Take \(\pi = \frac{22}{7}\)]
A
6.6 cm
B
8.8 cm
C
4.4 cm
D
2.2 cm
medium Difficulty
Verified Correct Answer: Option C
Step-by-Step Mathematical Solution
Length = \(\frac{\theta}{360}\) x 2\(\pi\)r
= \(\frac{72}{360} \times 2 \frac{22}{7} \times \frac{0.5}{3.5}\)
= 4.4
Source: Myschool Past Questions Archive (Record #57257)
Mathematics
WAEC / WASSCE 2019
Geometry and Trigonometry
Solution
Find the angle at which an arc of length 22 cm subtends at the centre of a circle of radius 15cm. [Take \(\pi = \frac{22}{7}\)]
A
70\(^o\)
B
84\(^o\)
C
96\(^o\)
D
156\(^o\)
medium Difficulty
Verified Correct Answer: Option B
Step-by-Step Mathematical Solution
L = \(\frac{\theta}{360} \times 2 \pi r\)
22 = \(\frac{\theta}{360} \times 2 \times \frac{22}{7} \times 15\)
\(\theta = \frac{22 \times 360 \times 7}{2 \times 22 \times 15}\)
\(\theta\) = 84\(^o\)
Source: Myschool Past Questions Archive (Record #57272)
Mathematics
WAEC / WASSCE 2019
Geometry and Trigonometry
Solution
A rectangular board has a length of 15cm and width x cm. If its sides are doubled, find its new area.
A
60x cm\(^2\)
B
45x cm\(^2\)
C
30x cm\(^2\)
D
15x cm\(^2\)
medium Difficulty
Verified Correct Answer: Option A
Step-by-Step Mathematical Solution
New are = (2 x 15) x (2 x \(x\))
= 60cm\(^2\)
Source: Myschool Past Questions Archive (Record #57274)
Mathematics
WAEC / WASSCE 2019
Geometry and Trigonometry
Diagram
Solution
In the diagram, POS and ROT are straight lines. OPQR is a parallelogram, |OS| = |OT| and ∠OST = 50^\circ. Calculate the value of ∠OPQ.
Attached Figure / Diagram
A
100\(^o\)
B
120\(^o\)
C
140\(^o\)
D
160\(^o\)
medium Difficulty
Verified Correct Answer: Option A
Step-by-Step Mathematical Solution
S\(O\)T = 180\(^o\) - (50 + 50)
= 80\(^o\)
P\(Q\)R = 80\(^o\)
= \(\frac{360^o - 160^o}{2}\) = 100\(^o\)
Source: Myschool Past Questions Archive (Record #57313)
Mathematics
WAEC / WASSCE 2019
Geometry and Trigonometry
Solution
The interior angles of a polygon are 3x\(^o\), 2x\(^o\), 4x\(^o\), 3x\(^o\) and 6x\(^o\). Find the size of the smallest angle of the polygon.
A
80\(^o\)
B
60\(^o\)
C
40\(^o\)
D
30\(^o\)
medium Difficulty
Verified Correct Answer: Option B
Step-by-Step Mathematical Solution
3\(x^o\) + 2\(x^o\) + 4\(x^o\) + 3\(x^o\) + 6\(x^o\) = 540\(^o\)
\(\frac{18x^o}{18} = \frac{540^o}{18}\)
\(x^o\) = 30\(^o\)
Smallest angle = 2 x 30\(^o\) = 60\(^o\)
Source: Myschool Past Questions Archive (Record #57323)
Mathematics
WAEC / WASSCE 2019
Geometry and Trigonometry
Solution
If tan x = \(\frac{3}{4}\), 0 < x < 90\(^o\), evaluate \(\frac{\cos x}{2 sin x}\)
A
\(\frac{8}{3}\)
B
\(\frac{3}{2}\)
C
\(\frac{4}{3}\)
D
\(\frac{2}{3}\)
medium Difficulty
Verified Correct Answer: Option D
Step-by-Step Mathematical Solution
y\(^2\) = 3\(^2\) + 4\(^2\)
y\(^2\) = 9 + 16
y = \(\sqrt{25}\)
= 5
\(\frac{\cos x}{2 \sin x} = \frac{4}{5} + 2 \times \frac{3}{5}\)
= \(\frac{4}{5} \times \frac{5}{6}\)
= \(\frac{2}{3}\)
Source: Myschool Past Questions Archive (Record #57365)
Mathematics
WAEC / WASSCE 2019
Geometry and Trigonometry
Solution
From the top of a vertical cliff 20m high, a boat at sea can be sighted 75m away and on the same horizontal position as the cliff. Calculate, correct to the nearest degree, the angle of depression of the boat from the top of the cliff.
A
56\(^o\)
B
75\(^o\)
C
16\(^o\)
D
15\(^o\)
medium Difficulty
Verified Correct Answer: Option D
Step-by-Step Mathematical Solution
Sin\(\theta = \frac{20}{75}\)
\(\theta = sin^{-1} (\frac{20}{75})\)
= 15\(^o\)
Source: Myschool Past Questions Archive (Record #57369)
Mathematics
WAEC / WASSCE 2019
Geometry and Trigonometry
Diagram
Solution
In the diagram, O is the centre of the circle of radius 18cm. If < zxy = 70\(^o\), calculate the length of arc ZY. [Take \(\pi = \frac{22}{7}\)]
Attached Figure / Diagram
A
11cm
B
22 cm
C
44 cm
D
80 cm
medium Difficulty
Verified Correct Answer: Option C
Step-by-Step Mathematical Solution
Z\({O}\)T = 2 x 70\(^o\) 140\(^o\)
Length = \(\frac{\theta}{360}\) x 2\(\pi\)r
\(\frac{140^o}{360} \times 2 \times \frac{22}{7}\) x 18
= 44cm
Source: Myschool Past Questions Archive (Record #57378)
Mathematics
WAEC / WASSCE 2019
Geometry and Trigonometry
Diagram
Solution
In the diagram, RT is a tangent to the circle at R, < PQR = 70\(^o\), < QRT = 52\(^o\), < QSR and < PRQ = x. Find the value of y.
Attached Figure / Diagram
A
70\(^o\)
B
60\(^o\)
C
52\(^o\)
D
18\(^o\)
medium Difficulty
Verified Correct Answer: Option C
Step-by-Step Mathematical Solution
∠QRT = ∠SRT = 52 (opposite angles)
∠SRT = y = 52 (alternate angles)
y = 52\(^o\)
Source: Myschool Past Questions Archive (Record #57379)
Mathematics
WAEC / WASSCE 2019
Geometry and Trigonometry
Diagram
Solution
In the diagram, PQ is parallel to RS, < QFG = 105\(^o\) and < FEG = 50\(^o\). Find the value of m.
Attached Figure / Diagram
A
130\(^o\)
B
105\(^o\)
C
75\(^o\)
D
55\(^o\)
medium Difficulty
Verified Correct Answer: Option D
Step-by-Step Mathematical Solution
50\(^o\) + m = 105\(^o\) (exterior angle of \(\triangle\)
m = 105\(^o\) - 50\(^o\)
m = 55\(^o\)
Source: Myschool Past Questions Archive (Record #57383)
Mathematics
WAEC / WASSCE 2019
Geometry and Trigonometry
Diagram
Solution
In the diagram, PQRS is a quadrilateral, < PQR = < PRS = 90\(^o\), |PQ| =3cm, |QR| = 4cm and |PS| = 13 cm. Find the area of the quadrilateral.
Attached Figure / Diagram
medium Difficulty
Verified Correct Answer: Option
Step-by-Step Mathematical Solution
In \(\triangle\)PQR
|PR|\(^2\) = |PQ|\(^2\) + |QR|\(^2\)
= 3\(^2\) + 4\(^2\)
|PR|\(^2\) = 9 + 16
|PR| = \(\sqrt{25}\) = 5cm
In \(\triangle\)PRS
|PS|\(^2\) = |PR|\(^2\) + |RS|\(^2\)
13\(^2\) = 5\(^2\) + |RS|\(^2\)
169 =25 + |RS|\(^2\)
|RS|\(^2\) = 169 - 25
= 144
|RS| = \(\sqrt{144}\) = 12cm
Area of quadrilateral PQRS = Area of \(\triangle\)PQR + Area of \(\triangle\)PQR + Area of \(\triangle\)PRS
= (\(\frac{1}{2} \times 3 \times 4\)) + (\(\frac{1}{2} \times 12 \times 5\))
= 6cm\(^2\) + 30cm\(^2\)
= 36cm\(^2\)
Source: Myschool Past Questions Archive (Record #58025)
Mathematics
WAEC / WASSCE 2019
Geometry and Trigonometry
Solution
The force of attraction F, between two bodies, varies directly as the product of their masses, \(m_1\) and m\(_2\) and inversely as the square of the distance, d, between them. Given that F = 20N, when m\(_1\) = 25kg, m\(_2\) = 10kg and d = 5m, find:
(I) an expression for F in terms of m\(_1\), m\(_2\) and d;
(ii) the distance, d for F = 30N, m\(_1\) = 7.5kg and m\(_2\) = 4kg
(b) Find the value of x in the diagram
medium Difficulty
Verified Correct Answer: Option
Step-by-Step Mathematical Solution
F \(\infty\) \(\frac{m_1m_ 2}{d^2}\)
F = \(\frac{km_1m_2}{d^2}\)
20 = \(\frac{k(25)(10)}{(25)}\)
\(\frac{10k}{10} = \frac{20}{10}\)
k = 2
(i) F = \(\frac{2m_1m_2}{d_2}\)
(ii) Since F = \(\frac{2m_1m_2}{d_2}\)
30 = \(\frac{2(7.5)(4)}{d^2}\)
30 \(\frac{60}{d^2}\)
d\(^2\) = \(\frac{60}{30}\)
d\(^2\) = 2
d = \(\sqrt{2}\)m
(b) Sum of angles = (n - 2) 180
= (5 - 2) 180
= 540\(^o\)
x + x + 20 + x + 60 + x + 40 + x + 80 = 540
5x + 200 = 540
5x = 540 - 200
\(\frac{5x}{5} = \frac{340}{5}\)
x = 68\(^o\)
Source: Myschool Past Questions Archive (Record #58032)
Mathematics
WAEC / WASSCE 2019
Geometry and Trigonometry
Solution
(a) Copy and complete the table of values for y = 2 cos x + 3 sin x for 0\(^o\) \(\geq\) x \(\geq\) 360\(^o\)
x
0\(^o\)
60\(^0\)
120\(^o\)
180\(^o\)
240\(^o\)
300\(^o\)
360\(^o\)
y
2.0
- 3.6
(b) Using a scale of 2cm to 60\(^o\) on the x-axis and 2cm to 1 unit in the y-axis, draw the graph of y = 2 cos x + 3 sin x for 0\(^o\) \(\geq\) 360\(^o\)
(c) Using the graph,
(i) Solve 2 cos x + 3 sin x = -1
(ii) Find, correct to one decimal place, the value of y when x = 342\(^o\)
medium Difficulty
Verified Correct Answer: Option
Step-by-Step Mathematical Solution
(a) When x = 60\(^o\)
y = 2cos 60\(^o\) + 3sin 60\(^o\)
y = 3.6
When x = 120\(^o\)
y = 2 cos 120\(^o\) + 3 sin 180\(^o\)
y = 1.6
When x = 180\(^o\)
y = 2 cos 180\(^o\) + 3 sin 180\(^o\)
y = 2
When x = 300\(^o\)
y = 2 cos 300\(^o\) + 3 sin 300\(^o\)
y = 1.6
when x = 360\(^o\)
y = 2 cos 360\(^o\) + 3 sin 360\(^o\)
y = 2
(b)
(c)(i) 1555.5\(^o\), 318\(^o\)
(ii) When x = 3.42\(^o\), y = 0.9\(^o\)
Source: Myschool Past Questions Archive (Record #58147)
Mathematics
WAEC / WASSCE 2019
Geometry and Trigonometry
Solution
In the diagram, \(\overline{RT}\) and \(\overline{RT}\) are tangent to the circle with centre O. < TUS = 68 ^\circ, < SRT = x, and < UTO = y. Find the value of x.
(b) Two tanks A and B am filled to capacity with diesel. Tank A holds 600 litres of diesel more than tank B. If 100 litres of diesel was pumped out of each tank, tank A would then contain 3 times as much diesel as tank B. Find the capacity of each tank.
medium Difficulty
Verified Correct Answer: Option
Step-by-Step Mathematical Solution
T\(O\)S = 68\(^o\) x 2
= 136\(^o\)
(Angle at centre is twice angle at circumference)
T\(R\) = 180\(^o\) - (90 + 68\(^o\))
= 180\(^o\) - 158\(^o\)
= 22\(^o\)
x = 2 x T\(R\)O = 2 x 22\(^o\) = 44\(^o\)
(b) Let the capacity of Tank B = x litres
Capacity of Tank A = x + 600 litres
If 100 litres is pumoed out of each tank then,
(x + 600) - 100 = 3(x - 100)
x + 500 = 3x - 300
500 + 300 = 3x - x
\(\frac{800}{2} = \frac{2x}{x}\)
x = 400 litres
Capacity of Tank A = 400 + 600
= 1,000 litres
Capacity of Tank B = 400 litres
Source: Myschool Past Questions Archive (Record #58175)
Mathematics
WAEC / WASSCE 2018
Geometry and Trigonometry
Diagram
Solution
In the diagram, PS and RS are tangents to the circle centre O. ∠PSR = 70°, ∠POR = m, and ∠PSR =n. Find ( m + n ).
Attached Figure / Diagram
A
110\(^o\)
B
135\(^o\)
C
165\(^o\)
D
225\(^o\)
medium Difficulty
Verified Correct Answer: Option C
Step-by-Step Mathematical Solution
In the diagram,
Thus, m = 2 x 55\(^o\) (is a bisector of obtuse
m = 110\(^o\)
n = \(\frac{1}{2}\) x 110\(^o\) (angle at centre = 2 x angle at circum)
n = 55\(^o\)
m + n = 110 + 55 = 165\(^o\)
Source: WAEC / JAMB / NECO Classroom Archive (Record #49510)