Test Index

JAMB Mathematics 2023 Paper

© africaexams.com

Question : 42

Total: 80

Calculate, correct to three significant figures, the length AB in the diagram above.

36.4 cm
36.1 cm
36.2 cm
36.3 cm

Solution:

Concept:

Use the sine rule for non-right-angled triangles to relate sides and opposite angles.

Explanation:

The sine rule states:

\frac{\sin A}{a} = \frac{\sin B}{b}

.

In the diagram, the side

43.2\text{ cm}

is opposite angle

82^\circ

, and

AB

is opposite angle

56^\circ

.

So:

\frac{\sin 82^\circ}{43.2} = \frac{\sin 56^\circ}{AB}

.

Cross-multiply:

AB \times \sin 82^\circ = 43.2 \times \sin 56^\circ

.

Thus:

AB = \frac{43.2 \times \sin 56^\circ}{\sin 82^\circ}

.

Calculate:

\frac{43.2 \times 0.8290}{0.9903} \approx 36.2\text{ cm}

.

Correct to three significant figures,

AB = 36.2\text{ cm}

.

Answer:

C.

36.2\text{ cm}

© africaexams.com

Go to Question:

Prev Question

Next Question