Trigonometry : Practical Applications

Study concepts, example questions & explanations for Trigonometry

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Example Questions

Example Question #1 : Vectors

Consider the following graphs where  begins at the origin and ends at  and .  Which of the following depicts the correct resultant of these two vectors.

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Possible Answers:

Screen shot 2020 08 27 at 1.33.16 pm

Screen shot 2020 08 27 at 1.32.16 pm

Screen shot 2020 08 27 at 1.31.51 pm

Screen shot 2020 08 27 at 1.32.49 pm

Correct answer:

Screen shot 2020 08 27 at 1.33.16 pm

Explanation:

To find the resultant we must sum the two vectors:

Now we must graph the resultant

Screen shot 2020 08 27 at 1.31.14 pm

Example Question #2 : Vectors

How many degrees above the x-axis is ?

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Possible Answers:


Correct answer:

Explanation:

First, we must understand what we are solving for.  We are solving for the angle that is formed by  and the x-axis.  To do this, we can extend a vector from the origin which stops directly under the end of .  We will call this new vector  and it will be 7 units long.  We will also extend a vector upwards that is perpendicular to the x-axis.  We will call this  and it will be 3 units long.

Screen shot 2020 08 27 at 2.26.24 pm

Now we can use the relationship that  where  is the adjacent side and  is the opposite side.

And so  is 23.2 degrees above the x-axis.

Example Question #2 : Vectors

Find the difference of the two vectors,  which ends at   and  ending at .

 

 

Possible Answers:

-

-

-

Correct answer:

Explanation:

When finding the difference of two vectors, you must subtract the x and y components separately.

Example Question #3 : Vectors

Which of the following is the correct depiction of the difference of vectors A and B?

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Possible Answers:

Screen shot 2020 08 27 at 1.43.44 pm

Screen shot 2020 08 27 at 1.43.37 pm

Screen shot 2020 08 27 at 1.43.50 pm

Screen shot 2020 08 27 at 1.43.01 pm

Correct answer:

Screen shot 2020 08 27 at 1.43.01 pm

Explanation:

To find the difference of two vectors we must consider the x and y components separately.

 

And then we must correctly graph this vector

Screen shot 2020 08 27 at 1.43.01 pm

Example Question #4 : Vectors

True or False: The magnitude of a vector is the length of the vector.

Possible Answers:

False

True 

Correct answer:

True 

Explanation:

When finding the magnitude of the vector, you use either the Pythagorean Theorem by forming a right triangle with the vector in question or you can use the distance formula.  This is much more clear considering the distance vector that the magnitude of the vector is in fact the length of the vector.

Example Question #1 : Bearing

Which of the following could represent an aeronautical bearing of ?

Possible Answers:

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Screen shot 2020 08 03 at 12.59.14 pm

Screen shot 2020 08 03 at 1.00.54 pm

Screen shot 2020 08 03 at 1.00.35 pm


Screen shot 2020 08 03 at 1.15.33 pm

Correct answer:

Screen shot 2020 08 03 at 1.00.35 pm

Explanation:

The correct image depicting an aeronautical bearing of  is 

Screen shot 2020 08 03 at 1.00.35 pm

This image begins at north, and moves  clockwise from it. 

Three of the given incorrect answers depict . The fourth incorrect answer does not represent a standard bearing convention as it is neither an acute angle, nor in the clockwise direction. That incorrect answer looks like:

Screen shot 2020 08 03 at 1.11.51 pm

Example Question #2 : Bearing

Which of the following diagrams could show a bearing of ?

 

Possible Answers:

Screen shot 2020 08 03 at 1.15.33 pm

Screen shot 2020 08 03 at 1.14.52 pm

Screen shot 2020 08 03 at 12.58.23 pm

Screen shot 2020 08 03 at 1.11.14 pm

Correct answer:

Screen shot 2020 08 03 at 1.15.33 pm

Explanation:

The bearing of a point B from a point A in a horizontal plane is defined as the acute angle made by the ray drawn from A through B with the north-south line through A. The bearing is read from the north or south line toward the east or west. Bearing is typically only represented in degrees (or degrees and minutes) rather than radians. To find , start in the south direction, then move  towards the west:

Screen shot 2020 08 03 at 1.15.33 pm

 

 

The other incorrect answer choices provided depict , and .

Example Question #1 : Bearing

The following diagram could represent which one of these practical scenarios?

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Possible Answers:

A helicopter traveling  at  miles per hour for  hours

An airplane traveling  at  miles per hour

A motorboat traveling  at  miles per hour for  hours

A race car traveling  at  miles per hour

Correct answer:

A motorboat traveling  at  miles per hour for  hours

Explanation:

This question and its answer choices give you a few clues to work with. First, we need to identify the bearing angle being shown. The options in the answer choices are either , or . Because the angle begins in the south direction and moves  towards the west, the correct bearing is . That means only two of the answer choices could be correct. We now need to understand how the  miles per hour corresponds to the problem. Notice that there is no answer choice that has the bearing of  and velocity of  miles per hour. Rather, we need to choose between  miles per hour for  hours or  miles per hour for  hours. Because  miles per hour for  hours corresponds to  (whereas the other option corresponds to only ), the correct answer is "A motorboat traveling  at  miles per hour for  hours."

Example Question #3 : Bearing

A ship moves in the direction  at a speed of  miles per hour for  hours. How far south and how far east is the ship from its starting position?

Possible Answers:

181.87 miles south and 105 miles east

30.31 miles south and 17.5 miles east

17.5 miles south and 30.31 miles east

105 miles south and 181.87 miles east

Correct answer:

181.87 miles south and 105 miles east

Explanation:

First, let's set up a diagram using the given information. This looks like this:

Screen shot 2020 08 03 at 2.07.54 pm 

Next, let's convert this info into a triangle so that we can use trigonometry to solve the problem. We need to calculate that the ship going  miles per hour for  hours will have traveled  miles. 

Screen shot 2020 08 03 at 2.12.15 pm

Now we can use trigonometry to determine the missing sides, s and e.

Therefore the ship has travelled 181.87 miles south and 105 miles east. 

Example Question #1 : Bearing

An airplane is traveling at a bearing of  from north for 330 kilometers. How far south and how far east is the plane from its starting point?

Possible Answers:

The airplane is 299.08 km south of its starting point and 139.46 km east of its starting point.

The airplane is 707.69 km south of its starting point and 139.46 km east of its starting point.

The airplane is 139.46 km south of its starting point and 299.08 km east of its starting point.

The airplane is 139.46 km south of its starting point and 707.69 km east of its starting point.

Correct answer:

The airplane is 139.46 km south of its starting point and 299.08 km east of its starting point.

Explanation:

First, let's incorporate the given information into a diagram. Start by labelling the plane's bearing of  along with its velocity 330km. Next, draw a line segment to complete the triangle and determine the measures of the angles of the triangle. We can determine the angle , we constructed the diagram such that there is a right angle, and finally we can find the third angle by taking 

Screen shot 2020 08 03 at 2.38.56 pm

The question is asking us how far south and how far east the plane is from its starting point, so we need to now use trigonometry to determine the lengths of the missing sides of the triangle. We will call these sides s for the southward distance and e for the eastward distance.

 km

 km

Therefore the airplane is 139.46 km south of its starting point and 299.08 km east of its starting point.

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