WAEC Mathematics 2019 Paper

Concept:The angle of depression from the top of the cliff is equal to the angle of elevation from the boat.This forms a right-angled triangle using the cliff height and the horizontal distance.Explanation:Let $\theta$ be the required angle of depression.Height of cliff $=$ opposite side $= 20$ m.Horizontal distance from the cliff $=$ adjacent side $= 75$ m.Using the tangent ratio:$\tan \theta = \frac{\text{opposite}}{\text{adjacent}} = \frac{20}{75}$$\theta = \tan^{-1}\left(\frac{20}{75}\right)$$\theta = \tan^{-1}(0.2667)$$\theta \approx 14.93^{\circ}$Correct to the nearest degree, $\theta = 15^{\circ}$.Answer:D. $15^{\circ}$