Chapter 4: Problem 39
Exer. 35-46: Sketch the graph of \(f\) $$f(x)=\log _{3}\left(x^{2}\right)$$
Short Answer
Expert verified
The graph of \( f(x) = \log_3(x^2) \) is even, passing through \((1,0)\) and \((-1,0)\), with asymptotes approaching \(-\infty\) near zero, symmetric about the y-axis.
Step by step solution
01
Understand the Function
The function given is \( f(x) = \log_{3}(x^2) \). This is a logarithmic function with base 3, which means it will be defined for \( x^2 > 0 \), or in simpler terms, when \( x eq 0 \).
02
Identify the Domain
Since \( x^2 > 0 \) for all \( x eq 0 \), the domain of \( f(x) = \log_{3}(x^2) \) includes all non-zero real numbers: \( x \in \mathbb{R} \setminus \{0\} \).
03
Behavior at Key Points
Calculate \( f(x) \) at key values of \( x \). For instance, at \( x=1 \), \( f(1) = \log_3(1^2) = 0 \), and similarly \( f(-1) = \log_3((-1)^2) = 0 \). This suggests \( x = 1 \) and \( x = -1 \) are points on the graph. Additionally, as \( x \) approaches 0, \( f(x) \) will tend towards \( -\infty \).
04
Symmetry of the Function
Observe that \( f(-x) = \log_3((-x)^2) = \log_3(x^2) = f(x) \). This indicates that the function is even, leading to symmetry about the y-axis.
05
Sketch the Graph
Using the information from previous steps, sketch the graph. It will pass through the points \((1,0)\) and \((-1,0)\), display symmetry about the y-axis, and tend toward \(-\infty\) as \( x \to 0^+ \) and \( x \to 0^- \). The graph will rise as \( |x| \) increases.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Graphing Logarithmic Functions
Graphing logarithmic functions, such as the one in our exercise, offers a unique insight into how logarithmic equations behave visually. The function of interest is \( f(x) = \log_{3}(x^2) \). This indicates that we're observing a logarithmic function with a base 3. Here's how you can sketch it:
- Plot key points: It helps to identify and plot essential points, such as \( (1, 0) \) and \( (-1, 0) \), because they tell us where the graph intersects the x-axis.
- Analyze behavior: Understand that as \( |x| \) becomes larger, \( f(x) \) increases upwards. This means the graph will continue growing as the absolute value of \( x \) moves away from zero.
- Understand the asymptotic behavior: As \( x \) approaches zero, \( f(x) \) will tend towards \( -\infty \), which helps to visualize the graph sloping sharply downward on either side of the y-axis.
Domain of a Function
The domain of a function represents all possible input values (x-values) for which the function is defined. For the function \( f(x) = \log_{3}(x^2) \), determining the domain requires understanding the constraints placed by the logarithmic and squared components.
- Consider the logarithm: Logarithms require positive arguments, so \( x^2 > 0 \).
- Analyze the squared term: Since \( x^2 \) is positive for all values except when \( x = 0 \), the function is undefined at \( x = 0 \).
Even Functions
Even functions possess a special property of symmetry around the y-axis. An even function satisfies the condition \( f(x) = f(-x) \) for all \( x \) in its domain. Upon inspecting the function \( f(x) = \log_{3}(x^2) \), you can see it is even for several reasons:
- Function relation: Since \( f(-x) = \log_{3}((-x)^2) = \log_{3}(x^2) = f(x) \), it clearly satisfies the even function condition.
- Graphical symmetry: The symmetry about the y-axis indicates that the graph of \( f(x) = \log_{3}(x^2) \) is a mirrored image when reflected over the y-axis.
Symmetry in Graphs
Symmetry in graphs is a fascinating concept where certain transformations leave the graph unchanged. In our function, \( f(x) = \log_{3}(x^2) \), there's symmetry about the y-axis due to its even nature.
- Identify symmetrical attributes: The even function property \( f(x) = f(-x) \) confirms this symmetry. Visually, this means the graph appears identical on both sides of the y-axis.
- Graphical implications: This symmetry implies that for every point \( (a, b) \) on the graph, there exists a point \( (-a, b) \) too.