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Find the period and graph the function. $$ y=5 \sec 2 \pi x $$

Short Answer

Expert verified
The period of the function is 1.

Step by step solution

01

Identify the Basic Secant Function

Start by recalling the general form of the secant function, which is given by \( y = a \sec(bx + c) + d \). In this equation, \( a \), \( b \), \( c \), and \( d \) determine different characteristics of the graph, such as amplitude, period, phase shift, and vertical shift. The function \( y = \sec(x) \) has a basic period of \( 2\pi \).
02

Determine the Coefficient of the Angle in the Function

In the given function, \( y = 5 \sec(2\pi x) \), the coefficient \( b \) in \( bx \) is \( 2\pi \). This coefficient is used to determine the period of the function.
03

Calculate the Period of the Function

The formula for the period of a \( \sec(bx) \) function is \( \frac{2\pi}{|b|} \). Substituting the value of \( b = 2\pi \), we get:\[ \text{Period} = \frac{2\pi}{|2\pi|} = 1 \]So, the period of the function \( y = 5 \sec(2\pi x) \) is 1.
04

Graph the Function Over One Period

To graph \( y = 5 \sec(2\pi x) \), first plot the corresponding cosine function \( y = 5 \cos(2\pi x) \), as secant is the reciprocal of cosine. Over one period from \( x = 0 \) to \( x = 1 \), the cosine function will complete one full cycle. Mark the points where the cosine function equals zero (\( x = 0.25 \) and \( x = 0.75 \)), leading to vertical asymptotes for the secant function. Using the symmetry and periodicity, sketch the secant function that oscillates and approaches these vertical lines.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Period of Secant Functions
When graphing secant functions, recognizing the period is fundamental. The period of a function is the minimum interval over which the function repeats itself. For standard trigonometric functions like sine and cosine, this period is typically \(2\pi\). However, with secant functions, especially when influenced by coefficients, you might notice a variation in this recurring pattern.
In the given exercise, we have the function \(y = 5 \sec(2\pi x)\). To find the period, observe the coefficient of \(x\), which is \(2\pi\). The formula to determine the period in secant functions is \( \frac{2\pi}{|b|}\), where \(b\) affects the period.
For this function, that calculation becomes \(\frac{2\pi}{2\pi} = 1\). This means the graph of \(y = 5 \sec(2\pi x)\) repeats every 1 unit, making it easier to predict its behavior over different intervals.
Properties of Trigonometric Functions
Trigonometric functions, including secant, embody certain universal properties that define their graphs and functionality. These characteristics help in understanding their transformations and behaviors under various modifications.
First, trigonometric functions are periodic, meaning they repeat at regular intervals. Second, they exhibit symmetry; for instance, secant functions possess even symmetry, which makes their graphs look the same on either side of the y-axis.
Another property worth noting is continuity. Functions like sine and cosine are continuous, but secant functions, due to their vertical asymptotes, appear discontinuous. These vertical asymptotes happen where the cosine function hits zero since secant is its reciprocal.
  • Amplitude: Determines the maximum and minimum extent of the function in the vertical direction. Secant doesn't have amplitude in the traditional sense as it ranges from negative infinity to positive infinity.
  • Vertical Shift: This will move the function up or down along the y-axis.
  • Phase Shift: This shifts the function left or right on the graph.
This understanding lays down the groundwork for plotting secant and other trigonometric functions.
Reciprocal Trigonometric Functions
Secant functions are part of the family known as reciprocal trigonometric functions. These functions arise when you take the reciprocal of the basic trigonometric functions.
The secant function by definition is \(\sec(x) = \frac{1}{\cos(x)}\). Thus, anywhere the cosine function equals zero, the secant function will have undefined values, leading to vertical asymptotes.
  • Secant and Cosine Relationship: Secant mirrors the cosine function where it is not zero, creating a depiction that waves with unnaturally high peaks and low valleys.
  • Graphical Representation: While graphing \(y = \sec(x)\), it proves useful to first plot \(y = \cos(x)\). This way, points where cosine crosses the x-axis can be marked, indicating vertical asymptotes in the secant graph.
Understanding secant as the reciprocal helps visualize its behavior and the importance of its relationship with the cosine function.
Vertical Asymptotes in Graphs
Secant functions feature vertical asymptotes; these are lines where the function shoots to positive or negative infinity. Asymptotes occur in secant functions when the base function, cosine in this case, becomes zero.
  • Identifying Asymptotes: In the function \(y = 5 \sec(2\pi x)\), vertical asymptotes appear whenever \(2\pi x = \frac{(2n + 1)\pi}{2}\), where \(n\) is an integer, since this is when the cosine function equals zero.
  • Graph Analysis: Visually, this appears as the secant function curve approaching but never touching these lines.
Vertical asymptotes split the graph into sections, each showing the secant's towering rise and sharp fall, demonstrating how these asymptotes provide structure to the periodic nature of the graph.

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Most popular questions from this chapter

Doppler Effect When a car with its horn blowing drives by an observer, the pitch of the horn seems higher as it approaches and lower as it recedes (see the figure on the next page). This phenomenon is called the Doppler effect. If the sound source is moving at speed \(v\) relative to the observer and if the speed of sound is \(v_{0}\) , then the perceived frequency \(f\) is related to the actual frequency \(f_{0}\) as follows: $$ f=f_{0}\left(\frac{v_{0}}{v_{0} \pm v}\right) $$ We choose the minus sign if the source is moving toward the observer and the plus sign if it is moving away. Suppose that a car drives at 110 \(\mathrm{ft} / \mathrm{s}\) past a woman standing on the shoulder of a highway, blowing its horn, which has a frequency of 500 \(\mathrm{Hz}\) . Assume that the speed of sound is 1130 \(\mathrm{ft} / \mathrm{s}\) . (This is the speed in dry air at \(70^{\circ} \mathrm{F}\) . (a) What are the frequencies of the sounds that the woman hears as the car approaches her and as it moves away from her? (b) Let \(A\) be the amplitude of the sound. Find functions of the form $$ y=A \sin \omega t $$ that model the perceived sound as the car approaches the woman and as it recedes.

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