Chapter 5: Problem 89
Determine the period and range of each function. $$y=-3 \csc (2 x-\pi)-4$$
Short Answer
Expert verified
The period is \pi\, and the range is \left(-\infty, -7\right] \cup \left[-1, \infty\right).
Step by step solution
01
Understanding the Cosecant Function
Recognize that the given function is related to the cosecant function. The general form of a cosecant function is \(y = a \csc(bx - c) + d\), where the parameters affect the period and vertical shift.
02
Identifying the Coefficients
From the given function \(y = -3 \csc(2x - \pi) - 4\), identify the coefficients: \(a = -3\), \(b = 2\), \(c = \pi\), and \(d = -4\).
03
Determining the Period
The period of the cosecant function is given by \frac{2\pi}{b}\. Here, \(b = 2\). Thus, the period is \frac{2\pi}{2} = \pi.\
04
Determining the Range
The range of the cosecant function is affected by the vertical shift and amplitude. Generally, the range of \(a \csc(x)\) is \left(-\infty, -|a|\right] \cup \left[|a|, \infty\right).\ Here, \(a = -3\), so the initial range is \left(-\infty, -3\right] \cup \left[3, \infty\right).\ After applying the vertical shift \(d = -4\), shift each part of the range down by 4 units: \left(-\infty, -7\right] \cup \left[-1, \infty\right).
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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, often denoted as \(\text{csc}(x)\), is one of the fundamental trigonometric functions. It is defined as the reciprocal of the sine function: $$\text{csc}(x) = \frac{1}{\text{sin}(x)}$$. This function is unique because it is undefined wherever the sine function is zero. This means \(\text{csc}(x)\) has vertical asymptotes at these points.
The general form of the cosecant function is: $$y = a \text{csc}(bx - c) + d$$. Each parameter plays a significant role in transforming the function:
The general form of the cosecant function is: $$y = a \text{csc}(bx - c) + d$$. Each parameter plays a significant role in transforming the function:
- \(a\): Amplitude, or the vertical stretch/compression.
- \(b\): Affects the period of the function.
- \(c\): Horizontal shift.
- \(d\): Vertical shift.
period of a function
The period of a trigonometric function is the interval after which the function repeats its values. For the general cosecant function \(y = a \text{csc}(bx - c) + d\), the period is influenced by the coefficient \(b\).
To find the period, use the formula: $$\text{Period} = \frac{2\text{Ï€}}{b}$$. For instance, in the function \(y = -3 \text{csc}(2x - \text{Ï€}) - 4\), we identify \(b = 2\). So, the period is calculated as:
\[\text{Period} = \frac{2\text{Ï€}}{2} = \text{Ï€}\].
This means every π units along the x-axis, the cosecant function will repeat its values, giving insights into its cyclical nature.
To find the period, use the formula: $$\text{Period} = \frac{2\text{Ï€}}{b}$$. For instance, in the function \(y = -3 \text{csc}(2x - \text{Ï€}) - 4\), we identify \(b = 2\). So, the period is calculated as:
\[\text{Period} = \frac{2\text{Ï€}}{2} = \text{Ï€}\].
This means every π units along the x-axis, the cosecant function will repeat its values, giving insights into its cyclical nature.
range of a function
The range of a trigonomic function refers to the set of all possible output values (y-values). For the cosecant function \(y = a \text{csc}(bx - c) + d\), the range primarily depends on the amplitude \(a\) and the vertical shift \(d\).
In its untransformed state, the range of \(\text{csc}(x)\) is °À(°À³Ù±ð³æ³Ùµ÷-∞ < y ≤ -1} ∪ \text{1 ≤ y < ∞}\). When transformed, \(a\) modifies this by scaling it vertically, and \(d\) shifts it up or down. For example, in the function \(y = -3 \text{csc}(2x - \text{Ï€}) - 4\):
°À(°À³Ù±ð³æ³Ùµ÷-∞ < y ≤ -7} ∪ \text{-1 ≤ y < ∞}\).
In its untransformed state, the range of \(\text{csc}(x)\) is °À(°À³Ù±ð³æ³Ùµ÷-∞ < y ≤ -1} ∪ \text{1 ≤ y < ∞}\). When transformed, \(a\) modifies this by scaling it vertically, and \(d\) shifts it up or down. For example, in the function \(y = -3 \text{csc}(2x - \text{Ï€}) - 4\):
- \(a = -3\) which scales the range to \(-3\).
- \(d = -4\) which shifts the entire range 4 units down.
°À(°À³Ù±ð³æ³Ùµ÷-∞ < y ≤ -7} ∪ \text{-1 ≤ y < ∞}\).
vertical shift in trigonometric functions
The vertical shift in a trigonometric function moves the entire graph up or down along the y-axis. In the general form \(y = a \text{csc}(bx - c) + d\), the parameter \(d\) represents the vertical shift.
A positive value of \(d\) moves the graph up, while a negative value shifts it downward. For example, in the function \(y = -3 \text{csc}(2x - \text{Ï€}) - 4\):
A positive value of \(d\) moves the graph up, while a negative value shifts it downward. For example, in the function \(y = -3 \text{csc}(2x - \text{Ï€}) - 4\):
- The \(d = -4\) indicates a vertical shift of 4 units downwards.