View Full Version : Trigonometry (bearings)
Kell
Aug 26, 2007, 08:30 PM
A boat sails form port on a bearing of 290 degrees for 130 nm. How far north is it form its starting point?
Clough
Aug 26, 2007, 11:06 PM
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reinsuranc
Aug 27, 2007, 05:07 AM
A boat sails form port on a bearing of 290 degrees for 130 nm. How far north is it form its starting point?
A 290 degree angle is equivalent to a -70 degree angle. Draw a -70 degree angle from the x axis, and call it theta. Let the length of the diagonal line be 130. Draw a line from the x axis to where the diagonal line ends; call the length of the second line y. sin(-70) = y/130. -.94 = y/130. y=-122.2 (rounded). This is 122.2 nm SOUTH from where it started.
galactus
Aug 27, 2007, 02:25 PM
Just use 130cos(290)
Or you can look at the diagram. 130sin(20). Same thing.
marium mustafa
Sep 30, 2009, 09:41 AM
(b) as close as possible to B means that the line BD is perpendicular to the 050 bearing line and so AB is a hypotenuse
So use the basic cosine ratio:
cos 50 = BD/280
BD = 280 cos 50
BD = 179.98
So after walking for 180 m he is as close to B as he is going to get on the 050 bearing