Trig
posted by Adam on .
Suppose you would like to cross a 200foot wide river in a boat. Assume that the boat can travel 35 mph relative to the water and that the current is flowing west at the rate of 5 mph. What bearing should be chosen so that the boat will land at a point exactly across from its starting point? Give your answer to the nearest tenth of a degree.

If it takes x hours to cross the river as intended, and
200ft = .06096 km
0.06096^2 + (5x)^2 = (35x)^2
x = 0.00175976
tanθ = 5*0.00175976 / 0.06096 = 0.14433
θ = 8.2°
hmm. or, with less calculation,
sinθ = 5/35 = 1/7
θ = 8.2°