Chapter 17: Problem 2
Find and sketch the image of the given region under \(w=e^{x}\). $$-1 \leqq x \leqq 0,0 \leq y \leq \pi / 2$$
Short Answer
Expert verified
The image is a circular sector in the first quadrant, radius
\(\frac{1}{e}\leq r\leq 1\), angle \(0\) to \(\frac{\pi}{2}\).
Step by step solution
01
Understand the problem
We are given a region defined by \[-1 \leq x \leq 0,\quad 0 \leq y \leq \frac{\pi}{2}\]and need to find and sketch the image of this region under the transformation \[w = e^z = e^{(x + iy)}.\]
02
Apply the transformation
Using the complex number transformation, express it in magnitude and argument:\[w = e^{x+iy} = e^x e^{iy} = e^x (\cos y + i \sin y).\]This means the image is a region in the complex plane with radius controlled by \(e^x\) and a full angle range from \(0\) to \(\frac{\pi}{2}\) due to \(y\).
03
Evaluate the range for the real axis
Evaluate the interval \(-1 \leq x \leq 0\):- For \(x = -1\), \(e^x = e^{-1} = \frac{1}{e}.\)- For \(x = 0\), \(e^x = e^0 = 1.\) Therefore, the magnitude of \(w\) ranges from \(\frac{1}{e}\) to \(1\).
04
Evaluate the range for the imaginary axis
The argument of \(w\) is given by \(y\):- For \(y = 0\), the argument is \(0\).- For \(y = \frac{\pi}{2}\), the argument is \(\frac{\pi}{2}\).Thus, the region describes the first quadrant arc from angle \(0\) to \(\frac{\pi}{2}\) in the complex plane.
05
Sketch the image
The image of the region is a circular sector in the complex plane:- Radius: \(\frac{1}{e} \leq r \leq 1\).- Angle: from \(0\) to \(\frac{\pi}{2}\).Sketch this as a sector in the first quadrant, originating from the origin with an outer arc extending between the radius values.
Unlock Step-by-Step Solutions & Ace Your Exams!
-
Full Textbook Solutions
Get detailed explanations and key concepts
-
Unlimited Al creation
Al flashcards, explanations, exams and more...
-
Ads-free access
To over 500 millions flashcards
-
Money-back guarantee
We refund you if you fail your exam.
Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!
Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Complex Transformation
Complex transformations change a complex number into another by applying a specified function. In our exercise, the transformation is given by the exponential function:
- The transformation is expressed as \[ w = e^z = e^{(x + iy)} \]where \(z = x + iy\) is the complex variable.
- In the exponential transformation, the complex number \(z\) is transformed into \(w\) by separating the real and imaginary components.
- Here, \( e^z \) implies converting \( e^x \) as the magnitude and \( e^{iy} \) as the direction (angle).
- The real part, \( e^x \), changes the distance from the origin, while the imaginary part provides the rotational angle, resulting in a new mapping of the original region.
Complex Plane
The complex plane, also known as the Argand plane, is a two-dimensional plane for representing complex numbers. Each complex number \(a + bi\) can be portrayed as a point or vector:
- The horizontal axis (real axis) denotes the real part of a complex number.
- The vertical axis (imaginary axis) stands for the imaginary part.
- The transformation \( w = e^z \) reshapes the region defined within the complex plane.
- Instead of treating complex numbers simply as a combination of real and imaginary parts, this plane allows them to be seen as geometric points which undergo dynamic transformations.
Circular Sector
A circular sector is a portion of a circle enclosed by two radii and an arc. It resembles a 'slice' of the circle. In complex analysis, transformations can map rectangular regions into unusual shapes like circular sectors, as seen in our example:
- The arc is bounded by angles, ranging from \(0\) to \(\frac{\pi}{2}\) provided in the given transformation, which influences the sector's shape.
- The radii are defined by the transformation's magnitude criteria: \( \frac{1}{e} \leq r \leq 1 \), which establishes the radial boundaries.