Answer:
Let us take Θ as measured zero straight across the river.
(draw a diagram)
If the current were zero, he would travel at 6 m/s at some angle Θ.
Now add the speed of the current, directly downstream at 5 m/s
His speed, directly across will be v^2 = 6^2 - 5^2 or v= 3.3 m/s
tan Θ = 5 / 3/.3 and Θ = 56.6 deg
Instead of travelling directly across he must choose an angle of 56.6 deg
from straight across
