document.write( "Question 1159690: 6. A ship leaves the Columbia bar with a bearing of S30° W and a speed of 15 knots. After 2 hours, the ship turns 90° towards the southeast. After 3 hours, maintaining the same speed, what is the bearing to the ship from the Columbia bar? \n" ); document.write( "
Algebra.Com's Answer #782741 by jim_thompson5910(35256)\"\" \"About 
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\n" ); document.write( "Diagram
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\n" ); document.write( "A = ship's starting point and the location of the Columbia Bar
\n" ); document.write( "B = ship's location 2 hours after leaving point A
\n" ); document.write( "C = ship's location 3 hours after leaving point B
\n" ); document.write( "D = point used to set up bearing of S30W\r
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\n" ); document.write( "\n" ); document.write( "1 knot = 1 nautical mile per hour
\n" ); document.write( "15 knots = 15 nautical miles per hour
\n" ); document.write( "After 2 hours, the ship travels a distance of 2*15 = 30 nautical miles. So AB = 30.
\n" ); document.write( "Similarly, BC = 45 since 3*15 = 45\r
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\n" ); document.write( "\n" ); document.write( "Angle DAB = 30 degrees. We start by facing directly south, then turn 30 degrees westward, which is what the notation \"S30W\" indicates. \r
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\n" ); document.write( "\n" ); document.write( "For more information and examples about compass bearings, see this page.\r
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\n" ); document.write( "\n" ); document.write( "For now, ignore point D. Focus solely on triangle ABC.
\n" ); document.write( "Triangle ABC is a right triangle with the 90 degree angle at point B. This is due to the fact that the ship turns 90 degrees to the southeast.\r
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\n" ); document.write( "\n" ); document.write( "tan(angle) = opposite/adjacent
\n" ); document.write( "tan(A) = BC/AB
\n" ); document.write( "tan(A) = 45/30
\n" ); document.write( "tan(A) = 1.5
\n" ); document.write( "A = arctan(1.5)
\n" ); document.write( "A = 56.3099324740202 You need to make sure your calculator is in degree mode
\n" ); document.write( "So angle BAC is roughly 56.3099324740202 degrees\r
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\n" ); document.write( "\n" ); document.write( "Subtract off the green angle 30 degrees to get
\n" ); document.write( "(angle BAC) - (angle DAB) = 56.3099324740202 - 30 = 26.3099324740202
\n" ); document.write( "which is the approximate measure of the red angle DAC.\r
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\n" ); document.write( "\n" ); document.write( "If we're situated at point A, face directly south, and turn roughly 26.3099324740202 degrees eastward, then we'll be looking directly at point C. \r
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\n" ); document.write( "\n" ); document.write( "Rounding to 4 decimal places, that would be roughly 26.3099; feel free to change the level of accuracy based off what your teacher instructs. \r
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\n" ); document.write( "\n" ); document.write( "The bearing to the ship from the Columbia Bar is approximately S 26.3099 E
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