Question

4(b). The height, h m, of a dock above sea level is given by h = 6+4cos(15p)°, 0<p<6. Find: (i) the value of h when p°=4; (ii) correct to two significant figures, the value of p° when h=9m.

Accepted Answer

(i) When p=4: h = 6+4cos(60°) = 6+4(0.5) = 8m.
(ii) When h=9: 9=6+4cos(15p)° → 3=4cos(15p)° → cos(15p)°=0.75 → 15p = cos⁻¹(0.75) = 41.4° → p = 41.4/15 ≈ 2.8 (2 s.f.).

WAEC Mathematics 2015 Theory — Question 8

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