I will be using the Law of cosine

a2=b2+c2-2bc*cos(deg)   

Example: would be if a car in the dessert was traveling 4.3m one  way then turn at 30 degrees and went to 7.2m another direction. 

If side b = 4.3m at an angle of 30 degrees and another side c =7.2m we use the law of cosine as such.

a2=4.32+7.22-2(4.3)(7.2)*cos(30)

a2=18.49+51.84-53.6243

a2=16.7057

once your answer you can now solve for side a. to do that you would need to take the square root of it.

a2=16.7057 will now be 

which should give us 4.08726

round to 4.1m

I think this would be how cell phones are tracked too.