Chapter 6: Problem 46
Sketch the graph of the equation. $$y=\tan ^{-1} 2 x$$
Short Answer
Expert verified
The graph of \( y = \arctan(2x) \) is a horizontally compressed version of \( y = \arctan(x) \). It has horizontal asymptotes at \( y = \pm \frac{\pi}{2} \).
Step by step solution
01
Understand the Inverse Tangent Function
The function given is \( y = \arctan(2x) \). \( \arctan(x) \) is the inverse of the \( \tan(x) \) function, which means it returns an angle whose tangent is \( x \). The range of \( \arctan(x) \) is \( \left(-\frac{\pi}{2}, \frac{\pi}{2}\right) \), and the domain is all real numbers. The graph is continuous, increasing, and approaches \( \frac{\pi}{2} \) and \( -\frac{\pi}{2} \) as \( x \to \infty \) and \( x \to -\infty \) respectively.
02
Identify the Effect of the Multiplier on x
The given function is \( y = \arctan(2x) \). This means \( x \) is scaled by 2. For the graph of \( y = \arctan(2x) \), this scaling horizontally compresses the graph towards the y-axis compared to \( y = \arctan(x) \). This means any features that occur for \( \arctan(x) \) will occur more quickly with respect to the x-axis.
03
Analyze Critical Points and Behavior
Identify some key points and behaviors for plotting: \( \arctan(0) = 0 \), so \( \arctan(2 \times 0) = 0 \). When \( x = 1 \), \( \arctan(2 \times 1) \approx \frac{\pi}{4} \). When \( x = -1 \), \( \arctan(2 \times (-1)) \approx -\frac{\pi}{4} \). As \( x \to \infty \), \( y \to \frac{\pi}{2} \) and as \( x \to -\infty \), \( y \to -\frac{\pi}{2} \).
04
Sketch the Graph
Begin graphing by marking \( (0,0) \) as a starting point. Indicate asymptotes at \( y = \pm \frac{\pi}{2} \). Plot a few points like \( (1, \frac{\pi}{4}) \) and \( (-1, -\frac{\pi}{4}) \). Draw a smooth curve through these points, showing the curve is increasing and approaches \( y = \frac{\pi}{2} \) and \( y = -\frac{\pi}{2} \) as asymptotic limits.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Graphing Functions
Graphing functions is a fundamental skill in understanding mathematical relationships. It allows us to visualize how one quantity depends on another by plotting the function on a coordinate grid. The function is typically represented as \( y = f(x) \) where each \( x \) value corresponds to a \( y \) value.
To graph any function:
To graph any function:
- Identify the type of function and specific characteristics such as symmetry, intercepts, and possible asymptotes.
- Select a range of \( x \) values and calculate corresponding \( y \) values.
- Plot these points on a graph and connect them to form a curve or line.
Inverse Tangent Function
The inverse tangent function, often written as \( y = \arctan(x) \), is an essential concept in trigonometry. It is the inverse of the tangent function and returns the angle whose tangent is \( x \). This function has certain characteristics:
- The range, or output, of \( \arctan(x) \) is limited to \( \left(-\frac{\pi}{2}, \frac{\pi}{2}\right) \), making it different from the tangent function, which repeats every \( \pi \).
- The domain, or input, includes all real numbers, providing a wide scope for input values.
- The graph is continuous and steadily increasing, with horizontal asymptotes at \( y = -\frac{\pi}{2} \) as \( x \) approaches \( -\infty \), and \( y = \frac{\pi}{2} \) as \( x \) approaches \( +\infty \).
Function Transformation
Function transformations modify the appearance of a function's graph without changing its fundamental nature.
For the equation \( y = \arctan(2x) \), the transformation involves scaling the input, which compresses the graph horizontally.
Here's how transformations work:
For the equation \( y = \arctan(2x) \), the transformation involves scaling the input, which compresses the graph horizontally.
Here's how transformations work:
- A multiplier inside the function, such as \( 2x \), affects the x-values, causing horizontal stretching or compression. In this case, \( x \) is replaced by \( 2x \), compressing the graph towards the y-axis. This causes the graph to approach asymptotic limits more quickly.
- Horizontal compression implies that all characteristics of the function occur sooner on the x-axis compared to the standard form.