Chapter 17: Problem 1
Find and sketch the image of the given region under \(w=e^{x}\). $$0 \leq x \leq 2,-\pi \leq y \leq \pi$$
Short Answer
Expert verified
The image is an annular region in the complex plane with inner radius 1 and outer radius \(e^2\).
Step by step solution
01
Understand the transformation
The transformation given is of the form \( w = e^z \), where \( z = x + iy \). Hence, \( w = e^x \cdot e^{iy} \). This means the transformation maps points \( (x,y) \) in the Cartesian plane to points in the complex plane.
02
Analyze the real part transformation
In \( w = e^{x+iy} \), the modulus \( |w| = e^x \). We see that \( x \) controls the magnitude of \( w \). Given the range \( 0 \leq x \leq 2 \), this maps to the magnitude range \( 1 \leq |w| \leq e^2 \).
03
Analyze the imaginary part transformation
The argument of \( w = e^{iy} \) gives us the angle in the complex plane. Since \( -\pi \leq y \leq \pi \), the angle range of \( w \) is from \(-\pi \) to \(\pi\), covering the entire semicircle in the complex plane.
04
Determine the shape of the image
Combining both analyses, the image under the transformation \( w = e^z \) is an annular region, with an inner radius of 1 and an outer radius of \( e^2 \). It extends over the angles \( -\pi \) to \( \pi \), covering a full circle from negative to positive real axis.
05
Sketch the image
To sketch, draw a circle centered at the origin with a radius ranging from 1 to \( e^2 \). This defines an annular region. The region spans the full circle because \( y \) covers all arguments between \(-\pi\) and \(\pi\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Complex Transformation
A complex transformation is a process that turns one shape or region in the complex plane into another. When we talk about a transformation like \( w = e^z \), we are mapping complex numbers \( z = x + iy \) to another complex number \( w \). This particular transformation involves both the real part \( x \) and the imaginary part \( y \).
Transformation functions are powerful,
Transformation functions are powerful,
- providing a way to manipulate regions in the complex domain.
- They often have applications in complex analysis, a field critical to engineering and physics.
- For instance, in our exercise, we're using the exponential function to transform a rectangular region into an annular region in the complex plane.
Conformal Mapping
Conformal mapping is a concept where transformations preserve angles. Although the shape of a region can change under a conformal map, angles between intersecting curves remain unchanged.
When applying the transformation \( w = e^z \), the mapping is conformal except at points where the function derivative is zero, which is not common in our specific scenario.
This preservation of angles
When applying the transformation \( w = e^z \), the mapping is conformal except at points where the function derivative is zero, which is not common in our specific scenario.
This preservation of angles
- allows complex functions to be useful in fields such as fluid dynamics and electromagnetism.
- Ensures that local geometrical structures within a region are maintained post-mapping.
- Provides a consistent way to understand transformations across different complex scenarios.
Complex Plane
The complex plane, also known as the Argand Plane, is a way of visualizing complex numbers geometrically. Each complex number \( z = x + iy \) is represented as a point, \( (x, y) \), with the real part \( x \) and the imaginary part \( y \). It's like a regular xy-coordinate plane, but with an added twist – literally!
Consider the exercise's region defined by \( 0 \leq x \leq 2 \) and \(-\pi \leq y \leq \pi \). This specifies a rectangular region in the complex plane.
The transformation \( w = e^z \)
Consider the exercise's region defined by \( 0 \leq x \leq 2 \) and \(-\pi \leq y \leq \pi \). This specifies a rectangular region in the complex plane.
The transformation \( w = e^z \)
- morphs this rectangle into an annular region.
- The real part determines the "distance" from the origin, as we transform \( |w| = e^x \).
- The imaginary part rotates these distances, covering angles from \(-\pi\) to \(\pi\).