Chapter 16: Problem 7
Sketch graphs of (a) \(y=\tanh x\) and (b) \(y=\operatorname{coth} x\) for values of \(x\) between \(-3\) and 3
Short Answer
Expert verified
\(y = \tanh x\) is S-shaped, \(y = \operatorname{coth} x\) has vertical asymptote at \(x=0\) with branches declining towards \(1\) for \(x>0\) and \(-1\) for \(x<0\).
Step by step solution
01
Understanding the Functions
The function \(y = \tanh x\) is the hyperbolic tangent function. It is defined as \(\frac{e^x - e^{-x}}{e^x + e^{-x}}\). The function \(y = \operatorname{coth} x\) is the hyperbolic cotangent function, defined as \(\frac{e^x + e^{-x}}{e^x - e^{-x}}\) with a vertical asymptote at \(x=0\).
02
Analyze the Behavior of \(y = \tanh x\)
The function \(y = \tanh x\) is an odd function that is continuous and differentiable everywhere. As \(x\to \infty\), \(\tanh x\) approaches 1, and as \(x\to -\infty\), \(\tanh x\) approaches -1. The function is symmetric around the origin.
03
Analyze the Behavior of \(y = \operatorname{coth} x\)
The function \(y = \operatorname{coth} x\) is defined for \(xeq 0\) with a vertical asymptote at \(x=0\). For \(x>0\), \(\operatorname{coth} x\) approaches 1 as \(x\to \infty\), and for \(x<0\), \(\operatorname{coth} x\) approaches -1 as \(x\to -\infty\).
04
Sketch the Graph of \(y = \tanh x\)
Plot a curve that starts from -1 as \(x\to -3\), passes through the origin, and approaches 1 as \(x\to 3\). The graph is S-shaped and increases steadily but slowly at larger \(|x|\) values.
05
Sketch the Graph of \(y = \operatorname{coth} x\)
Plot two curves indicating the hyperbolic cotangent. For \(x>0\), the curve starts from a value just above 1 at \(x = 0^+\) and declines towards 1 as \(x\to 3\). For \(x<0\), it starts at a large negative value and increases towards -1 as \(x\to -3\). The graph is undefined at \(x=0\) due to a vertical asymptote.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding \( \tanh x \)
The hyperbolic tangent function, denoted as \( \tanh x \), is an important hyperbolic function that models the relationship between exponential functions in a unique way. The formula is given by:
- \( \tanh x = \frac{e^x - e^{-x}}{e^x + e^{-x}} \)
- It is an odd function, which means it is symmetric about the origin.
- For any real number \( x \), \( \tanh x \) gives a value between -1 and 1.
Exploring \( \coth x \)
The hyperbolic cotangent function, \( \coth x \), is another intriguing function defined as:
- \( \coth x = \frac{e^x + e^{-x}}{e^x - e^{-x}} \)
- It is defined everywhere except at \( x = 0 \), where it has a vertical asymptote.
- For positive \( x \), \( \coth x \) approaches 1 as \( x \) increases, and for negative \( x \), it approaches -1 as \( x \) decreases.
- Above or below 1 for most parts of its domain, depending on the direction of \( x \).
Graphing Hyperbolic Functions
The graphical representation of hyperbolic functions like \( \tanh x \) and \( \coth x \) reveals their distinct behaviors and trends. Visualizing these functions on a graph provides insight into:
- **Shapes and Symmetry**: The \( \tanh x \) graph is S-shaped and passes through the origin, displaying symmetry about the y-axis. Meanwhile, \( \coth x \) shows two separate branches due to its asymptote at \( x = 0 \).
- **Range and Limit Behavior**: \( \tanh x \) remains bounded between -1 and 1 for all \( x \), indicating a limiting behavior as \( |x| \) becomes large. Conversely, \( \coth x \) diverges as it approaches the asymptote, with its values extending beyond the range of \( \tanh x \).
- **Smoothness and Continuity**: \( \tanh x \) is continuous everywhere, while \( \coth x \) is continuous except where it speaks with infinity at \( x = 0 \).