Graphing Trigonometric Functions

Oct 13, 2025 by wbrum.org 123 views

Introduction

In this article, we will explore the graphs of two trigonometric functions, $f(\theta) = 3 \cos (\theta + \pi)$ and $h(\theta) = \cos (\theta)$ . We will examine how the graph of $f$ compares to the graph of $h$ , focusing on the effects of the constant multiple and phase shift on the graph.

The Graph of $f(\theta) = 3 \cos (\theta + \pi)$

The graph of $f(\theta) = 3 \cos (\theta + \pi)$ is a transformation of the graph of $y = \cos x$ . The constant multiple of 3 stretches the graph vertically by a factor of 3, while the phase shift of $\pi$ shifts the graph to the left by $\pi$ units.

Vertical Stretch

The vertical stretch of the graph of $f$ is a result of the constant multiple of 3. This means that the amplitude of the graph is increased by a factor of 3. In other words, the maximum value of the graph is 3, and the minimum value is -3.

Phase Shift

The phase shift of $\pi$ units to the left is a result of the addition of $\pi$ to the argument of the cosine function. This means that the graph of $f$ is shifted to the left by $\pi$ units compared to the graph of $h$ .

The Graph of $h(\theta) = \cos (\theta)$

The graph of $h(\theta) = \cos (\theta)$ is a standard cosine curve. The graph has a maximum value of 1 and a minimum value of -1. The graph is symmetric about the origin and has a period of $2\pi$ .

Comparison of the Graphs

The graph of $f(\theta) = 3 \cos (\theta + \pi)$ is a transformation of the graph of $h(\theta) = \cos (\theta)$ . The graph of $f$ has a vertical stretch of 3 and a phase shift of $\pi$ units to the left. This means that the graph of $f$ is taller and narrower than the graph of $h$ , and it is shifted to the left by $\pi$ units.

Key Differences

There are several key differences between the graphs of $f$ and $h$ :

Amplitude: The graph of $f$ has a maximum value of 3 and a minimum value of -3, while the graph of $h$ has a maximum value of 1 and a minimum value of -1.
Period: The graph of $f$ has a period of $2\pi$ , while the graph of $h$ has a period of $2\pi$ .
Phase Shift: The graph of $f$ is shifted to the left by $\pi$ units compared to the graph of $h$ .

Conclusion

In conclusion, the graph of $f(\theta) = 3 \cos (\theta + \pi)$ is a transformation of the graph of $h(\theta) = \cos (\theta)$ . The graph of $f$ has a vertical stretch of 3 and a phase shift of $\pi$ units to the left. This means that the graph of $f$ is taller and narrower than the graph of $h$ , and it is shifted to the left by $\pi$ units.

Graphing the Functions

To graph the functions, we can use a graphing calculator or a computer algebra system. We can also use a table of values to help us graph the functions.

Table of Values

Here is a table of values for the functions:

$\theta$	$f(\theta) = 3 \cos (\theta + \pi)$	$h(\theta) = \cos (\theta)$
0	-3	1
$\pi/2$	0	0
$\pi$	-3	-1
$3\pi/2$	0	0
$2\pi$	3	1

Graphing the Functions

Using the table of values, we can graph the functions. The graph of $f$ is a taller and narrower version of the graph of $h$ , and it is shifted to the left by $\pi$ units.

Final Thoughts

References

[1] "Trigonometry" by Michael Corral
[2] "Calculus" by Michael Spivak

Appendix

Here is some additional information that may be helpful:

Graphing Trigonometric Functions: There are several ways to graph trigonometric functions, including using a graphing calculator or a computer algebra system.
Table of Values: A table of values can be used to help us graph trigonometric functions.
Graphing the Functions: We can use a graphing calculator or a computer algebra system to graph the functions.
Q&A: Comparing the Graphs of Trigonometric Functions =====================================================

Frequently Asked Questions

In this article, we will answer some frequently asked questions about comparing the graphs of trigonometric functions.

Q: What is the difference between the graphs of $f(\theta) = 3 \cos (\theta + \pi)$ and $h(\theta) = \cos (\theta)$ ?

A: The graph of $f(\theta) = 3 \cos (\theta + \pi)$ is a transformation of the graph of $h(\theta) = \cos (\theta)$ . The graph of $f$ has a vertical stretch of 3 and a phase shift of $\pi$ units to the left.

Q: How does the graph of $f$ compare to the graph of $h$ in terms of amplitude?

A: The graph of $f$ has a maximum value of 3 and a minimum value of -3, while the graph of $h$ has a maximum value of 1 and a minimum value of -1. This means that the graph of $f$ is taller and narrower than the graph of $h$ .

Q: How does the graph of $f$ compare to the graph of $h$ in terms of period?

A: The graph of $f$ has a period of $2\pi$ , while the graph of $h$ has a period of $2\pi$ . This means that the graph of $f$ has the same period as the graph of $h$ .

Q: How does the graph of $f$ compare to the graph of $h$ in terms of phase shift?

A: The graph of $f$ is shifted to the left by $\pi$ units compared to the graph of $h$ .

Q: Can you provide a table of values for the functions?

A: Yes, here is a table of values for the functions:

$\theta$	$f(\theta) = 3 \cos (\theta + \pi)$	$h(\theta) = \cos (\theta)$
0	-3	1
$\pi/2$	0	0
$\pi$	-3	-1
$3\pi/2$	0	0
$2\pi$	3	1

Q: How can I graph the functions?

A: You can use a graphing calculator or a computer algebra system to graph the functions. You can also use a table of values to help you graph the functions.

Q: What are some key differences between the graphs of $f$ and $h$ ?

A: There are several key differences between the graphs of $f$ and $h$ :

Amplitude: The graph of $f$ has a maximum value of 3 and a minimum value of -3, while the graph of $h$ has a maximum value of 1 and a minimum value of -1.
Period: The graph of $f$ has a period of $2\pi$ , while the graph of $h$ has a period of $2\pi$ .
Phase Shift: The graph of $f$ is shifted to the left by $\pi$ units compared to the graph of $h$ .