Answer:
1753.67 m
Step-by-step explanation:
Using the law of cosine
After 2.9 hours, the first plane has moved 730*2.9=2117 m, let this be a
The second plane has moved 550*2.9=1595 m, let this be b
The angle between them is 111-56.8=54.2, let this be
c=1753.67 m