A boater wants to head straight across a river that has a current of 3km/hr. If the top speed of the boat in still water is 4km/hr, find the direction the boat must travel into the current to go straight across the river. How fast is the boat going straight across the river?

Answer 1

Assume current is moving due south(270o).

Vb = 4 - 3i.
tanA = -3/4 = -0.75
A = -36.9o = 36.9o South of East.
Vb = 4/cos36.9 = 5 km/h = Velocity of
boat.

The boat must travel 5 km/h @ 36.9o North of East.