
vectors help?
Hey first off I hope this is the right section topost in.
Anyways this is the question I was given I'm having trouble figurring out where I am going wrong on part c) . "In his rowboat, Pierre heads directly across a river at a speed of 10Km/hr. The river is flowing at 6 Km/hr."
a) what is the resultant speed of the river
answer=11.6km/hr
b) What angle will the resultant path of the boat make with the shoreline?
answer= 59degrees
c) if the river is 120 meters wide how far downstream will pierre land on the opposite side?
answer = 72meters (this is from the back of the book)
I am unsure how they got this I tried using sine law since I have all 3 angles and a given side but I keep getting 199 meters as my answer.
If anyone could help it really be appreciated(Nod)

1) The resultant speed of the river?
2) Which angle is 59.036 degrees? More specifically, is tan(59.036º) = river/downstream or is tan(59.036º) = downstream/river
3) Logically, the rowing is faster than the river. The correct result cannot be greater than 120m. Rough estimate? 120 * 6/10 = 72ish without any trig. It may be exact in this case, but there is not much need to count on that, since you should be learning some trigonometry.

ahh makes more sense now using the 59degrees i got the angle of 31 and 120 tan 31degrees is 72.1
thank you very much :)