Homework Help: Trig

Posted by Adam on Sunday, November 18, 2012 at 5:17am.

Suppose you would like to cross a 200-foot 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.

Trig - Steve, Sunday, November 18, 2012 at 3:13pm
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°

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