Chapter 7: Problem 30
7–52 Find the period and graph the function. $$y=5 \csc 3 x$$
Short Answer
Expert verified
Period: \(\frac{2\pi}{3}\); graph requires plotting asymptotes at \( x = \frac{n\pi}{3} \) and stretching waves vertically by 5.
Step by step solution
01
Identify the Parent Function
The given function is \( y = 5 \csc 3x \). The parent function is \( \csc x \), which is the reciprocal of \( \sin x \). It has vertical asymptotes where \( \sin x = 0 \).
02
Determine the Coefficient Effect
In the function \( y = 5 \csc 3x \), the coefficient 5 implies an amplitude stretch for the cosecant waves. The 3 multiplies x, affecting the period of the function.
03
Calculate the Period
The period of a \( \csc bx \) function is \( \frac{2\pi}{b} \). Here, \( b = 3 \), so the period is \( \frac{2\pi}{3} \).
04
Identify Key Points and Asymptotes
Cosecant has asymptotes where the sine function is zero. In \( y = \csc 3x \), asymptotes occur at \( 3x = n\pi \), where \( n \) is an integer, hence at \( x = \frac{n\pi}{3} \).
05
Graph the Function
Plot the vertical asymptotes at every \( \frac{n\pi}{3} \) on the x-axis. Sketch the basic shape of \( \csc x \) between these asymptotes to represent one cycle over \( \frac{2\pi}{3} \). The waves peak outwards from these asymptotes and stretch vertically by a factor of 5.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Cosecant Function
The cosecant function, denoted as \( \csc x \), is a trigonometric function that is the reciprocal of the sine function. Mathematically, this means \( \csc x = \frac{1}{\sin x} \). As it is derived from the sine function, the cosecant function shares some properties but also has some unique characteristics.
- Domain: The domain of \( \csc x \) consists of all real numbers except where \( \sin x = 0 \), because division by zero is undefined.
- Range: The range of \( \csc x \) is all real numbers greater than or equal to 1 and less than or equal to -1, because these are the values achievable by the reciprocal of the sine function.
- Period: The parent function \( \csc x \) has a period of \( 2\pi \), meaning it repeats itself every \( 2\pi \) units along the x-axis.
Function Graphing
Graphing functions like \( y = 5 \csc 3x \) involves a few key steps. To accurately sketch these transformations, you should recognize the effect of different coefficients in the function's equation.
- Amplitude and Vertical Stretch: The coefficient multiplied by the \( \csc x \) function affects how the graph stretches vertically. In \( y = 5 \csc 3x \), the '5' makes the "waves" of the graph stretch outwards from the x-axis by a factor of 5. This doesn't affect asymptotes but alters the height of peaks.
- Period Adjustment: The term '3x' in \( \csc 3x \) compresses the period to \( \frac{2\pi}{3} \). This means the function completes one full cycle every \( \frac{2\pi}{3} \) units, as opposed to the parent function's \( 2\pi \).
Vertical Asymptotes
Vertical asymptotes are a significant characteristic of the cosecant function. They occur at values where the sine function equals zero since \( \csc x \) involves taking the reciprocal of \( \sin x \). This results in divisions by zero, which are undefined, hence vertical asymptotes.
- Identifying Asymptotes: For the generic \( \csc bx \) function, vertical asymptotes occur where \( b \cdot x = n\pi \) for integer \( n \), equivalent to the sine function's zeros.
- Specific Example: For \( y = 5 \csc 3x \), the vertical asymptotes are at \( x = \frac{n\pi}{3} \) because these are the points where \( \sin 3x = 0 \). Thus, the function is undefined at these x-values.