Posted by brittney on .
A river is 2000 ft wide and flowing at 6 mph from north to south. A woman in a canoe starts on the eastern shore and heads west at her normal paddling speed of 2 mph. In what direction (measured clockwise from north) must she aim her canoe? How long will it take her to go directly across the river? Justify and explain your reasoning.

trigonometry 
Henry,
1. tanAr = 6/2 = 3.0,
Ar = 71.6 Deg = Reference angle.
A = 180 + Ar = 180 + 71.6 = 251.6 Deg.
Da = 180  71.6 = 108.4 Deg.,CCW =
Direction she should aim her canoe.
2. d = V*t,
t = d/V = (2000/5280) / 2 = 0.1894 h =
11.4 min. 
trigonometry 
Steve,
The only problem here is that when drawing your reference triangle, the westward speed was 2 and the downstream speed was 6, so you could take the tangent.
When rowing upstream, the 2 mph speed is along the hypotenuse, She can't row the required 2√10 = 6.32 mph needed to end up with a westward speed of 2 mph.