Chapter 3: Problem 72
Problems \(66-72\) go back to the theory. Create a function \(y(x)\) that has its maximum at a rough point and its minimum at an endpoint.
Short Answer
Expert verified
Use \( y(x) = 1 - |x| \) on \([-1, 1]\) to have maximum at cusp and minimum at endpoints.
Step by step solution
01
Identify the Requirements
We need to create a function \( y(x) \) such that it has a maximum at an internal point (not smooth, possibly a cusp or discontinuity) and a minimum at an endpoint of the interval. A common function type that has a cusp is the absolute value function, and it might be useful here.
02
Choose a Suitable Function
Consider the simple absolute value function \( y(x) = |x| \), which has a cusp at the origin and is continuous. This function has a sharp point at \( x = 0 \).
03
Define the Interval for the Function
Since the minimum is required to be at an endpoint, we decide on an interval such as \([-1, 1]\). This will make it easier to identify the endpoints and apply any modifications.
04
Verify Maximum and Minimum Points
For the function \( y(x) = |x| \) on \([-1, 1]\): - The minimum occurs at the endpoints, \( x = -1 \) and \( x = 1 \), where \( y(x) = 1 \).- The function has a cusp at \( x = 0 \), which becomes the maximum point at \( y(0) = 0 \).
05
Adjust and Ensure Conditions Are Met
Consider a modified form \( y(x) = 1 - |x| \) on \([-1, 1]\) to swap conditions,- The maximum is now at the cusp, \( x = 0 \) where the value is \( y(0) = 1 \).- The minimum occurs at \( x = -1 \) and \( x = 1 \) with \( y(x) = 0 \).This function meets the problem requirements.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Absolute Value Function
An absolute value function is a fundamental mathematical concept represented by the notation \( y(x) = |x| \). The absolute value of a number is its distance from zero on the number line, without considering direction. Thus, it is always non-negative.
- Graphical Representation: The graph of \( y(x) = |x| \) is V-shaped and has a vertex at the origin (0,0), forming a sharp point known as a cusp. This trait makes the absolute value function unique as it is continuous but not differentiable at this point.
- Key Properties: The function has two linear segments. For \( x > 0 \), it behaves like \( y(x) = x \), while for \( x < 0 \), it acts as \( y(x) = -x \). Therefore, \( y(x) \) transitions abruptly at \( x = 0 \). This discontinuity in the slope is why it is a popular choice when designing functions with special maximum or minimum conditions.
Maximum and Minimum Points
Finding the maximum and minimum points of a function involves determining where the function reaches its highest or lowest values within a given domain.
- Maximum Point: This occurs where the value of the function is higher compared to its surroundings. In the context of the absolute value function \( y(x) = 1 - |x| \), the peak, or cusp, at \( x = 0 \) becomes the maximum point. Here, the function evaluates to \( y(0) = 1 \), which is the highest value on the interval specified.
- Minimum Point: The minimum values are found at the endpoints of the interval. For the specified interval \( [-1, 1] \), these points are \( x = -1 \) and \( x = 1 \) where the function evaluates to zero, making them the lowest points.
Piecewise Functions
Piecewise functions provide a versatile way to define functions that have different expressions based on the input value.
- Definition: A piecewise function is written as a series of conditional equations. This allows the function to "change its rule" depending on which interval of values \( x \) is in. \( y(x) = |x| \) is inherently piecewise because it toggles between \( y(x) = x \) when \( x \) is non-negative and \( y(x) = -x \) when \( x \) is negative.
- Use in Variable Conditions: Such functions are particularly useful in scenarios where different behavior is required at different ranges of \( x \). For example, setting a maximum at a specific point and minimum at the endpoints as seen with \( y(x) = 1 - |x| \).