Answer:
Step-by-step explanation:
According to the diagram,
A = 90° + 25° = 115°
dc/dt = 29 km/min
distance after 5 min
c = 29 x 5 = 145 km
Use cosine rule
a² = b² + c² - 2bc Cos A
a² = 6² + c² -12cCos 115
a² = 36 + c² - 5 c .... (1)
When c = 145 km
a² = 36 + 145 x 145 - 5 x 145
a² = 21061 - 725
a = 142.6 km
Differentiate equation (1) with respect to a.
2a da/dt = 2c dc/dt + dc/dt
2 x 142.6 x da/dt = 2 x 145 x 29 + 29
285.2 da/dt = 8439
da/dt = 29.6 km/min
