A boat travels at a constant speed parallel to a coastline that is approximately a straight line. An observer on the coast at point P uses radar to find the distance to the boat when the boat makes an angle of 35 degrees with the coastline. Then, 5 seconds later,the observer finds the distance to the boat when it makes an angle of 70 degrees with the coast line.
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The angle at point A is 35 because the lines are parallel. The angle at point P is 70 and the angle at point B must then be: 180 - 70 - 35 = 75.
You have then three angles and two distances. Find the trigonometric equation that gives the third distance AB and you get the result. I am not going to calculate it for you, you must learn to do it yourself.
Incidentally, finding a position by taking two bearing, or finding a distance, is called, a "running fix." A ship would do it, sighting e.g. a lighthouse, knowing its course and speed, using parallel rulers. ... well, that was before the GPS! ;-)
You have then three angles and two distances. Find the trigonometric equation that gives the third distance AB and you get the result. I am not going to calculate it for you, you must learn to do it yourself.
Incidentally, finding a position by taking two bearing, or finding a distance, is called, a "running fix." A ship would do it, sighting e.g. a lighthouse, knowing its course and speed, using parallel rulers. ... well, that was before the GPS! ;-)