Chapter 17: Problem 4
Find the image of the given line under the mapping \(f(z)=z^{2}\) $$ y=0 $$
Short Answer
Expert verified
The real axis is mapped to itself under the transformation \(f(z) = z^2\).
Step by step solution
01
Understanding the Problem
We are asked to find the image of the line described by the equation \(y=0\), which is the real axis in the complex plane, under the mapping \(f(z) = z^2\). This means we need to determine what the real axis becomes when each of its points is squared by the function \(f(z)\).
02
Expressing Points on the Real Axis
A point on the real axis can be expressed as \(z = x + iy\), where \(y = 0\). Thus, points on the real axis can be written as \(z = x\), where \(x\) is a real number.
03
Applying the Mapping Function
We apply the mapping function \(f(z) = z^2\) on each point of the real axis. Substituting \(z = x\) into the function gives \(f(x) = (x)^2 = x^2\).
04
Describing the Image
Since \(f(x) = x^2\) is real for any real \(x\), the image of the real axis under this transformation is the set of real numbers \(x^2\), which is also the real axis. It suggests that the real axis is mapped onto itself.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Complex Mapping
Complex mapping involves a function that takes complex numbers as inputs and transforms them into another set of complex numbers. It's essential in complex analysis, where each complex number is often visualized as a point in the complex plane. This makes it easier to understand transformations geometrically.
Complex mapping often involves a function of the form \(f(z)\), where \(z\) is a complex number expressed as \(z = x + iy\). Here, \(x\) and \(y\) are real numbers, and \(i\) is the imaginary unit with the property \(i^2 = -1\). The transformation defined by the function changes the position of points in this two-dimensional plane, allowing us to observe how different structures, like lines or curves, are transformed.
Complex mapping often involves a function of the form \(f(z)\), where \(z\) is a complex number expressed as \(z = x + iy\). Here, \(x\) and \(y\) are real numbers, and \(i\) is the imaginary unit with the property \(i^2 = -1\). The transformation defined by the function changes the position of points in this two-dimensional plane, allowing us to observe how different structures, like lines or curves, are transformed.
- This approach can show us whether a set of points in the complex plane remains the same or takes on a new form under the transformation.
- For example, mapping a line or a circle in complex space could result in stretching, rotating, or otherwise altering these shapes.
Real Axis
The real axis is a critical concept in complex analysis. It refers to the horizontal axis in the complex plane and consists of all complex numbers of the form \(x + 0i\), effectively reducing to the real numbers. In this context, the real axis functions like the familiar number line, but situated in a plane where every point represents a complex number.
When examining complex mappings, it's often useful to observe how they affect the real axis:
When examining complex mappings, it's often useful to observe how they affect the real axis:
- The real axis can serve as a reference when a complex function is applied, as we can easily track changes by looking at how real points are mapped.
- Understanding the transformation of the real axis can give us insights into the behavior of more complex points in the complex plane.
Transformation
In complex analysis, a transformation specifies how complex numbers are altered by a function. This process is akin to taking basic shapes or lines within the complex plane and moving them to new positions based on the function's rule.
A transformation can do many things, such as:
A transformation can do many things, such as:
- Distorting shapes: It can bend or twist curves and lines, stretching some sections while compressing others.
- Preserving structure: In some cases, like with the squaring function, certain structures (like the real axis) can experience changes that maintain their basic form.
Squaring Function
The squaring function is a fundamental transformation in the realm of complex functions. Defined as \(f(z) = z^2\), it involves squaring each component of a complex number. If \(z = x + iy\), applying the squaring function results in:
\[f(z) = (x + iy)^2 = x^2 - y^2 + 2xyi\]
For real numbers (those along the real axis where \(y = 0\)), this simplifies to \(f(x) = x^2\), meaning:
\[f(z) = (x + iy)^2 = x^2 - y^2 + 2xyi\]
For real numbers (those along the real axis where \(y = 0\)), this simplifies to \(f(x) = x^2\), meaning:
- Points not only stay on the real axis post-transformation, but each point is moved such that a real negative remains a real positive when squared.
- This results in a stretching effect where the entire set of real numbers remains on the real axis after being squared.