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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)

< 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}}