Answer:
588 m
Step-by-step explanation:
The Law of Cosines is useful for finding the distance unknown distance 'c' when triangle sides 'a' and 'b' and the angle C between them are known.
c = √(a² +b² -2ab·cos(C))
c = √(400² +250² -2(400)(250)cos(128°)) ≈ 587.905 . . . m
Point Z is about 588 meters from the starting point.
__
Additional comment
It is often useful to use (x, y) = (North, East) coordinates in such calculations. This lets the calculator use distance and bearing directly. It looks "backward" on a coordinate plane, but the math works out. If you flip the figure over the line y=x, it will correspond to what you expect to see on a map.
