The diagram below shows a helicopter hovering at point H, 380 m vertically above a lake. Point A is the point on the surface of the lake, directly below the helicopter. Minta is swimming at a constant speed in the direction of point Minta observes the helicopter from point C as she looks upward at an angle of 25°. After 15 minutes, Minta is at point B and she observes the same helicopter at an angle of 40°.

Angle of depression = 90° - angle of elevation = 90° - 25° = 65° (A1)

Let AC = x tan 25° = $\frac{380}{x}$ x = $\frac{380}{\tan 25°}$ = 812.8... m = 813 m (2 sf) (A2)

(M1) for correct trigonometric equation (A1) for correct answer

Let AB = y tan 40° = $\frac{380}{y}$ y = $\frac{380}{\tan 40°}$ = 452.8... m

BC = AC - AB = 812.8... - 452.8... = 360.0 m (3 sf) (A3)

(M1) for correct trigonometric equation for AB (M1) for subtracting AB from AC (A1) for final answer with correct units