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| Question 813233:  A plane leaves an airport and travels 2500 mi. due West, then turns 38 degrees to the south and travels 240 mi to a second airport.  What is the displacement of the 1st airport from the 2nd airport? Round to 3 decimal places.  It asks for Magnitude and Direction.
 Answer by TimothyLamb(4379)
      (Show Source): 
You can put this solution on YOUR website! use the law of cosines to find the third side of the triangle ---
 a^2 = b^2 + c^2 - 2bc cos(I)
 where:
 b = 2500
 c = 240
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 but first find the included angle I
 I = 180 - 38 = 142 degrees
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 a^2 = 2500^2 + 240^2 - 2*2500*240*cos(142)
 a^2 = 6.25e6 + 5.76e4 - 1.2e6*(-0.7880107)
 a^2 = 6.25e6 + 5.76e4 + 9.456129e5
 a^2 = 7.2532129e6
 a = 2693.179
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 the airplane arrives at ap2 at a distance of 2693.179 miles from ap1.
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 now use the law of sines to find the smaller angle J of the triangle (ap1, turn-point, ap2):
 sin(J)/j = sin(I)/i
 sin(J)/240 = sin(142)/2693.179
 sin(J)= sin(142)240/2693.179
 sin(J)= (0.6156614)240/2693.179
 sin(J)= 0.054864
 J = arcsin(0.054864)
 J = 3.1450587 degrees
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 direction from ap2 to ap1 is:
 90 - 3.1450587 = 86.854941 ~= 86.855 degrees true north bearing
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 Answer:
 the vector from ap2 to ap1 is:
 Direction: 86.855 degrees true north
 Magnitude: 2693.179 miles
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