Two cars leave from the same point (A) and travel along a straight road, which are at angle of 78° to each other. If their speeds are 120 km/h (truck) and 90 km/h (car) respectively, how far apart will they be after one half hour?
a. Draw a diagram.
b. Distance = speed x time

Question

Two cars leave from the same point (A) and travel along a straight road, which are at angle of 78° to each other. If their speeds are 120 km/h (truck) and 90 km/h (car) respectively, how far apart will they be after one half hour? 
a. Draw a diagram.
b. Distance = speed x time

anonymous · Answer

Distance traveled by car 1 =  60
Distance traveled by car 2 =  45

Now, we can use the rule of cosines,

$ \sqrt{60^2 +45^2- 2\times\cos 78^\circ\times60 \times  45 } = \cdots $

anonymous · Answer

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anonymous · Answer

How did you get the distance? Since you both have different answers?

anonymous · Answer

Law of cosines:$$c ^{2} = a ^{2} + b ^{2} - 2abcos(\gamma)$$
So:
sqrt(60^2 + 30^2 - 2*30*60*cos(78)) = ~61

anonymous · Answer

why 30 lauriy? Am I missing something ...

anonymous · Answer

Sorry not 30 but 45...
sqrt(60^2 + 45^2 - 2*45*60*cos(78)) = ~67.1

anonymous · Answer

Uhm- I still don't understand how the distance go calculated? Like, how did you get 60, and 45? what steps? I understand the cos law, Thanks

anonymous · Answer

120km/h means 120 in 1 hour. So if he only has half an hour, he will do 60 km.