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April 22nd, 2009, 07:38 AM   #1
 
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trigonometry bearings problem

A helicopter pilot flies in the direction 147 degrees and lands when she is 12 km south of her starting point. How far did she fly?
How do you solve this/approach this problem?
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April 22nd, 2009, 01:26 PM   #2
 
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Re: trigonometry bearings problem

At 147 degrees, will [s]he not be NORTH of the starting point, albeit also westbound?
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April 22nd, 2009, 02:16 PM   #3
 
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Re: trigonometry bearings problem

Presumably it's 147 degrees true, i.e. clockwise from north.

Draw a compass rose and conclude that 147 degrees true is equivalent to 57 degrees clockwise from east.

So you must find the length of hypotenuse of a right-angled triangle, if one angle is 57 degrees and the side opposite is 12 km.
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October 16th, 2009, 03:07 PM   #4
 
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Re: trigonometry bearings problem

http://twitpic.com/lsl3r

1) find x. You do this by 180-147 = 33 degrees. (you just found one of the angles formed by the triangle)
2) Now that you know that angle, you can use trigonometry. In this case, its cos.
3) Cos = adjacent/hypotenuse = 12/y
4) Now you solve algebraically

Cos (33) = 12/y
y Cos 33 = 12
y = 12/Cos 33
y = 14.3 km
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