Question 1173231
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Hi  
Two boats leave a harbour at the same time and head out at an angle of 35o to each other
Boat A is travelling at 45 km/h and boat B is travelling at 52 km/h. 
How far apart are the two boats after two hours?
Viewing the boats traveling forming a  Right Triangle ∠A = 35°     
<img src=" http://upload.wikimedia.org/wikipedia/commons/thumb/6/6f/Rtriangle.svg/200px-Rtriangle.svg.png ">
one boat travels 90m (along b), the other 104m(along c)
Distance apart will be a on the picture
C^2 = a^2 + b^2
(104)^2 = a^2 + (90)^2
10816= a^2 + 8100 
10816 - 8100 = a^2
2716 = a^2 
a = 52.115km
Assuming the travel would result in a Right Triangle may not be the case:
Yes, Best to use cosine Law to cover all the bases.
{{{sqrt(90^2 + 104^2 - 2*90*104cos(35))}}} = 62.234km
In this case, travel didn't end up representing the model of a right Triangle.
Wish You the Best in your Studies.