Alright, for this question it is important to remember the Law of Sines, which is sin*a/A = sin*b/B = sin*c/C, in which the lowercase letters are the angles and the uppercase letters are the sides opposing the angles.
Before we use that, however, we need to set up the picture, and as we do that, we can also find all of the angles we will need. Based on this question, we know that the farthest boat (boat 1) is 20 degrees below the plane's horizon and that the other boat (boat 2) is 35 degrees below the plane's horizon. From this, we can make triangles to connect the plane to the boats to give us some more info about the question. (Picture 1)
Now we have set up the triangles, we can see that there are two 90 degree angles that will help us find out the degrees of the remaining angles. We can do this because we know that the sum of the angles in a triangle always equals 180 degrees. (Picture 2)
Now, we can begin to use the Law of Sines. We will start with the triangle that connects the plane to the closest boat (boat 2) because we know that the plane is 3000 ft above sea level. from that, we can begin to set up our first proportion (picture 3). Next, we solve for x which means cross multiplying to get 3000*sin(90) = x*sin(55) which leaves us with x being roughly 3662.323
Finally, we put the number we just found into the drawing to have a little breather step before continuing (picture 4). For the last part, we are focusing on the middle triangle, which will give us the distance between the two boats when we are done. We use the Law of Sines once again to set up the proportions (picture 5) before cross multiplying again to get 3662.323*sin(35)=y*sin(20), which should simplify to get y to equal roughly 6141.808 ft, which should be the distance between the two boats!Â
