math
posted by Daniel .
A kayaker paddles across a river at a constant speed of 4 miles per hour and a bearing of N 60 degrees E. Which current vector results in the kayaker's actual speed being 5.9 miles per hour and the kayakers actual direction being N 70 degrees E.

If we let
u = 4.0 @ N60E = (3.464,2.000)
w = 5.9 @ N70E = (5.544,2.018)
we want v such that
u+v = w
That should help.