Answer:
2.05 mi
Explanation:
I don't see a figure, so I am guessing that the plane is 1.7 miles above the ground.
Let x = distance of observer 1 from that point
y = distance of observer 2 from that point
Tan 48 = 1.7/x and tan 73 = 1.7/y
x tan 48 = 1.7 y tan 73 = 1.7
x = 1.7/tan 48 y = 1.7/tan 73
x + y = distance between the observers
x + y = 1.7/tan 48 + 1.7/tan 73
= 2.05 mi