Question 1013987
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Law of sines or cosines: Two cars leave the city at the same time and travel along straight roads that leave the city at 
an angle of 80 degree angle. One car is traveling at a rate of 60 mph and the other at a rate of 70 mph. 
How far apart will the cars be after 1 hour and 30 minutes?
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<U>Law of cosines</U>.    See the lesson <A HREF=http://www.algebra.com/algebra/homework/Trigonometry-basics/Proof-of-the-Law-of-Cosines-revisited.lesson>Proof of the Law of Cosines revisited</A> in this site.


One side of the triangle is 60 mph * 1.5 hours =  90 miles.
The other side is           70 mph * 1.5 hours = 105 miles.
The angle between these sides is 80°.

Hence, the third side is 

{{{sqrt(90^2 + 105^2 - 2*90*105*cos(80^o))}}} = 125.87 miles.

It is the distance between the cars after 1 hour and 30 minutes.
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