The angle subtended on a diameter of a circle is always 90º.
So if we consider the line between the two lighthouses to be a diameter of a semicircle, then as long as the angle formed by the two lines of sight to the lighthouses is less than 90º the skipper will be outside the semi-circle.
If the angle is greater than 90º .....
The skipper of a boat knows that the water is too shallow
to bring his boat inside a “danger semicircle” that
goes from lighthouse to lighthouse. How can the angle
between his sightings of the two lighthouses help him
decide when he is entering the danger zone?
1 answer