The pilot makes a big triangle with her flight path. The longest side will be her distance from the start as the crow flies.
Use the Law of Cosines (deg mode on a calculator):
c^2 = a^2 + b^2 - 2ab(cos C)
C = 170 degrees (only a 10 deg correction from 180)
a = 685 x 1.5 = 1027.5 miles
b = 685 x 2 = 1370 miles
It doesn’t matter which side is a and which side is b.
Now plug in the values and solve for c. Hope this helps.