WAEC Mathematics Past Questions & Answers - Page 233

1,161.

The diagram shows the position of three ships A, B and C at sea. B is due north of C such that |AB| = |BC| and the bearing of B from A = 040°. What is the bearing of A from C

A.

040o

B.

070o

C.

110o

D.

290o

Correct answer is D

< ABC = 40° (alternate angles)

\(\therefore\) < ACB = \(\frac{180° - 40°}{2}\)

= 70°

\(\therefore\) Bearing of A from C = 360° - 70° 

= 290°

1,162.

From the diagram above. ABC is a triangle inscribed in a circle center O. ∠ACB = 40o and |AB| = x cm. calculate the radius of the circle.

A.

\(\frac{x}{sin 40^o}\)

B.

\(\frac{x}{cos 40^o}\)

C.

\(\frac{x}{2 sin 40^o}\)

D.

\(\frac{x}{2 cos 40^o}\)

Correct answer is C

No explanation has been provided for this answer.

1,163.

From the top of a cliff 20m high, a boat can be sighted at sea 75m from the foot of the cliff. Calculate the angle of depression of the boat from the top of the cliff

A.

14.9 o

B.

15.5 o

C.

74.5 o

D.

75.1 o

Correct answer is A

\(\tan x = \frac{20}{75} = 0.267\)

\(x = \tan^{-1} 0.267 = 14.93°\)

\(\approxeq\) 14.9°

1,164.

If \(tan x = \frac{1}{\sqrt{3}}\), find cos x - sin x such that \(0^o \leq x \leq 90^o\)<

A.

\(\frac{\sqrt{3}+1}{2}\)

B.

\(\frac{2}{\sqrt{3}+1}\)

C.

\(\frac{\sqrt{3}-1}{2}\)

D.

\(\frac{2}{\sqrt{3}-1}\)

Correct answer is C

\(\cos x = \frac{\sqrt{3}}{2}\)

\(\sin x = \frac{1}{2}\)

\(\cos x - \sin x = \frac{\sqrt{3} - 1}{2}\)

1,165.

If y varies inversely as x\(^2\), how does x vary with y?

A.

x varies inversely as y2

B.

x varies inversely as √y

C.

x varies directly as y2

D.

x varies directly as y

Correct answer is B

\(y \propto \frac{1}{x^2}\)

\(y = \frac{k}{x^2}\)

\(x^2 = \frac{k}{y}\)

\(x = \frac{\sqrt{k}}{\sqrt{y}}\)

Since k is a constant, then \(\sqrt{k}\) is also a constant.

\(\therefore x \propto \frac{1}{\sqrt{y}}\)