Question 211660
<pre><font size = 4 color = "indigo"><b>
{{{drawing(400,100,-100,1300,0,70,
locate(1150,3,boat), locate(5,30,60), locate(500,10,x),
triangle(0,0,0,60,1144.9,0)  )}}}

To show the angle of depression, draw
a horizontal line at the top of the tower:

{{{drawing(400,100,-100,1300,0,70,locate(5,30,60), locate(500,10,x),
locate(1150,3,boat), line(-500,60,500,60),
triangle(0,0,0,60,1144.9,0)  )}}}

The angle between that horizontal and the 
line of sight to the boat is 3°

{{{drawing(400,100,-100,1300,0,70,locate(250,58,"3°"),
locate(1150,3,boat), line(-500,60,500,60),locate(5,30,60), locate(500,10,x),
triangle(0,0,0,60,1144.9,0), arc(0,60,10,-10,190,360) )}}}

Now by alternate interior angles the angle in the right
corner of the triangle is also 3°

{{{drawing(400,100,-100,1300,0,70,locate(250,58,"3°"), locate(800,13,"3°"),
locate(1150,3,boat), line(-500,60,500,60),locate(5,30,60), locate(500,10,x),
triangle(0,0,0,60,1144.9,0), arc(0,60,10,-10,190,360) )}}}

Now 60 is the opposite side to the angle 3° 
at the bottom right corner, and x is the adjacent side.

So we know to use tangent

tan(3°) = {{{60/x}}}

Multiply both sides by x

x*tan(3°) = 60

x = {{{60/tan("3°")}}}

x = {{{1144.868201}}}

or about 1145 feet.

Edwin</pre>