SOLUTION: I am trying to work out the area that my fish finder is covering at different depths under my boat. The angle it sends the beam down is 55 degrees. My question is at 10, 20, 30 40

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Question 857177: I am trying to work out the area that my fish finder is covering at different depths under my boat. The angle it sends the beam down is 55 degrees. My question is at 10, 20, 30 40 metres what is the diameter of the circle.
Regards Chris

Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
I am trying to work out the area that my fish finder is covering at different depths under my boat. The angle it sends the beam down is 55 degrees. My question is at 10, 20, 30 40 metres what is the diameter of the circle.
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55 degs is the included angle, --> 27.5 degs either side of center.
The radius (on the bottom) over the depth = tan(27.5)
r = d*tan(27.5) meters
r = 10*tan(27.5) =~ 5.2 meters
etc
radius =~ 1/2 the depth
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Area+=+pi%2Ar%5E2