Trigonometry : Practical Applications

Study concepts, example questions & explanations for Trigonometry

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Example Questions

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Example Question #1 : Bearing

Three ships are positioned in the following way: Ship A is 240 miles due west of Ship C, and Ship B is due south of Ship C. Ship B bears  from Ship A. How far is Ship B from Ship A? How far is Ship B from Ship C? What is the bearing from Ship A to Ship B?

Possible Answers:

Distance from Ship A to Ship B: 640.67 miles

Distance from Ship B to Ship C: 594.02 miles

Bearing from Ship B to Ship A: 

Distance from Ship A to Ship B: 594.02 miles

Distance from Ship B to Ship C: 640.67 miles

Bearing from Ship B to Ship A: 

Distance from Ship A to Ship B: 640.67 miles

Distance from Ship B to Ship C: 594.02 miles

Bearing from Ship B to Ship A: 

Distance from Ship A to Ship B: 594.02 miles

Distance from Ship B to Ship C: 640.67 miles

Bearing from Ship B to Ship A: 

Correct answer:

Distance from Ship A to Ship B: 640.67 miles

Distance from Ship B to Ship C: 594.02 miles

Bearing from Ship B to Ship A: 

Explanation:

To solve this problem, begin with a diagram, and label all known information. We know that we can label two angles as  and one length as 240. Then, by deductive reasoning, we can label another angle as  because .

Screen shot 2020 08 03 at 3.33.07 pm

Next, we need to use trigonometry to find the answers to each question we're being asked. To find the distance AB, set up

Next, we can find the distance BC. There are two ways to do this since we know two angles of the triangle, but either way you need to use the tangent function.

Finally, we are asked to find the bearing from Ship B to A. Be careful, because in the initial problem we are given the Bearing from Ship A to Ship B. While the angle will remain the same, the direction is different because we are starting at a different initial point (B instead of A). With B as your starting point, A is north and west. Therefore the bearing from Ship B to Ship A is .

 

Therefore the correct distance between Ships A and B is 640.67 miles, the distance between ships B and C is 594.02 miles, and the bearing from Ship B to Ship A is  .

Example Question #22 : Practical Applications

Three cruise ships are situated as follows: Sea Terraformer is 200 miles due north of Wave Catcher, and Island Pioneer is 345 miles due east of Wave Catcher. What is the bearing from Island Pioneer to Sea Terraformer, and what is the bearing from Sea Terraformer to Island Pioneer?

Possible Answers:

Bearing from Island Pioneer to Sea Terraformer: 

Bearing from Sea Terraformer to Island Pioneer: 

Bearing from Island Pioneer to Sea Terraformer: 

Bearing from Sea Terraformer to Island Pioneer: 

Bearing from Island Pioneer to Sea Terraformer: 

Bearing from Sea Terraformer to Island Pioneer: 

Bearing from Island Pioneer to Sea Terraformer: 

Bearing from Sea Terraformer to Island Pioneer: 

Correct answer:

Bearing from Island Pioneer to Sea Terraformer: 

Bearing from Sea Terraformer to Island Pioneer: 

Explanation:

Begin by diagramming the given information; you'll see that the three ships create a right triangle. To solve the question, we need to find the unknown angles of the triangle, then frame our answers as the proper bearings. 

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First let's solve for the topmost angle in the diagram, which we'll call .

By alternate interior angles, the other diagrammed angle will also be equal to .

Now, put your cursor on Island Pioneer, and see if you need to move north or south, and then east or west to get to Sea Terraformer. You need to move north, then west. Therefore the bearing between Island Pioneer and Sea Terraformer is . Now put your cursor on Sea Terraformer and complete the same process to get to Island Pioneer; you'll go south, then east. Therefore the bearing from Sea Terraformer to Island Pioneer is .

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