Graphing Secant and Cosecant

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Trigonometry › Graphing Secant and Cosecant

Questions 1 - 8
1

Give the equation of the following graph.

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Explanation

Looking at our graph, we can tell that the period is . Using the formula

where is the coefficient of and is the period, we can calculate

This eliminates one answer choice. We then retrun to our graph and see that the amplitude is 3. Remembering that the amplitude is the number in front of the function, we can eliminate two more choices.

We then examine our graph and realize it contains the point . Plugging 0 into our two remaining choices, we can determine which one gives us 4 for a result.

2

Considering the general form of the cosecant transformation function , what does each letter, (A, B, C, and D) correspond to?

A = Phase Shift , B = Period , C = Amplitude, D = Vertical Shift

A = Amplitude , Period , C = Vertical Shift, D = Phase Shift

A = Amplitude , B = Period , C = Phase Shift, D = Vertical Shift

A = Amplitude , Period , C = Phase Shift, D = Vertical Shift

Explanation

Since cosecant is a reciprocal of sine, it uses the same general formula of the sine function with the letters corresponding to the same transformations. Note that while A does correspond to amplitude, the cosecant function extends infinitely upwards and downwards so there is no amplitude for the graphs.

3

True or False: Amplitude must be considered when graphing the transformation of a secant graph.

True

False

Explanation

When looking at the graph of , it extends infinitely upwards and downwards from each local maximum and minimum. This will be true for all transformed secant graphs as well. Due to this, there is no amplitude for secant graphs. However, secant is the reciprocal of cosine graphs which do rely on amplitude for transformations. For this reason amplitude must be considered as a vertical shift.

4

Which of the following is the graph of ?

Screen shot 2020 08 28 at 9.41.54 am

Screen shot 2020 08 28 at 9.42.14 am

Screen shot 2020 08 28 at 9.44.10 am

Screen shot 2020 08 28 at 9.43.58 am

Explanation

In order to graph , recall that . First consider the graph .

Screen shot 2020 08 28 at 9.41.54 am

Now anywhere this graph crosses the x-axis a vertical asymptote will form for the graph because the denominator of will be equal to zero and the function will be undefined. At each maximum and minimum of , the graph of will invert at that point.

Screen shot 2020 08 28 at 9.42.05 am

And then we are left with the graph of .

Screen shot 2020 08 28 at 9.42.14 am

5

Which of the following is the graph of ?

Screen shot 2020 08 27 at 4.21.20 pm

Screen shot 2020 08 27 at 4.22.39 pm

Screen shot 2020 08 27 at 4.22.28 pm

Screen shot 2020 08 27 at 4.23.26 pm

Explanation

Knowing that the graph of is

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we can use the general form of the cosecant transformation equation, , and apply these transformations. We can ignore because in this case . In this case and so our period is:

Period =

Period =

Period =

is the normal period for cosecant graphs and so we do not have to worry about lengthening or shortening the period. and so we need to apply a phase shift of . This will cause our graph to shift left a total of units.

Screen shot 2020 08 27 at 4.20.00 pm

Lastly, we must apply the transformation for , so we will have an upward vertical shift of 1 unit.

Screen shot 2020 08 27 at 4.21.10 pm

The application of these transformations leaves us with our graph of .

Screen shot 2020 08 27 at 4.21.20 pm

6

Which of the following is the graph for ?

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Screen shot 2020 08 27 at 4.29.27 pm

Explanation

In order to understand the graph of secant, recall that . First consider the graph of .

Screen shot 2020 08 27 at 4.30.58 pm

Anywhere this graph crosses the x-axis a vertical asymptote will form for the graph because the denominator of will be equal to zero and the function will be undefined. At each maximum and minimum of , the graph of will invert at that point.

Screen shot 2020 08 27 at 4.31.03 pm

And then we are left with the graph .

Screen shot 2020 08 27 at 4.31.08 pm

7

Which of the following is the graph of ?

Screen shot 2020 08 28 at 9.34.10 am

Screen shot 2020 08 28 at 9.39.38 am

Screen shot 2020 08 28 at 9.37.58 am

Screen shot 2020 08 28 at 9.39.52 am

Explanation

Knowing that the general form of the graph is:

Screen shot 2020 08 28 at 9.34.10 am

We can use the general form of the cosecant transformation equation, , and apply these transformations. because secant graphs extend infinitely upwards and downwards and does not have an amplitude, we must think of the secant graph being a reciprocal of the cosine graph. So we will consider for cosine.

Screen shot 2020 08 28 at 9.34.16 am

We will shift our secant graph to invert at the maximums and minimums of the cosine graph.

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Next, we will factor in order to get our equation into the form .

And so . We can now solve for our period,

Period =

Period =

Period =

This shortens our original period of to .

Screen shot 2020 08 28 at 9.36.17 am

Now we must consider . This will give us a phase shift of units to the left. Since our period has also been shortened this does not change the graph visually. in this case so we do not need to consider a vertical shift.

Screen shot 2020 08 28 at 9.37.58 am

And we are left with the graph of .

8

This is the graph of what function of x?

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Explanation

is shown in red, and is shown in blue.

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