Chapter 17: Problem 37
In Problems 35-38, find all values of \(z\) satisfying the given equation. $$ e^{z-1}=-i e^{2} $$
Short Answer
Expert verified
All values of \(z\) are \(z = 3 + i\left(-\frac{\pi}{2} + 2k\pi\right)\) for any integer \(k\).
Step by step solution
01
Write the Equation in Exponential Form
We start by recognizing that \[ e^{z-1} = -i e^2 \]is an exponential equation. Our goal is to express both sides in a comparable exponential form, which means treating \(-i\) as an exponential.
02
Express \(-i\) Using Euler's Formula
Recall that any complex number can be expressed in exponential form using Euler's formula: \[ -i = e^{i\left(-\frac{\pi}{2}\right)} \]Notice that \(-i\) is on the negative imaginary axis, corresponding to an angle of \(-\frac{\pi}{2}\) or equivalently \(-\frac{\pi}{2} + 2k\pi\) for any integer \(k\).
03
Combine Exponential Parts
Substitute \(-i\) in exponential form into the original equation:\[ e^{z-1} = e^{i\left(-\frac{\pi}{2} + 2k\pi\right)} e^2 \]which simplifies to:\[ e^{z-1} = e^{2 + i\left(-\frac{\pi}{2} + 2k\pi\right)} \]
04
Equate Exponents
Since the bases of the exponentials on both sides are the same, the exponents must be equal. Thus, we have:\[ z-1 = 2 + i\left(-\frac{\pi}{2} + 2k\pi\right) \]
05
Solve for \(z\)
Rearrange the equation from Step 4 to solve for \(z\):\[ z = 2 + 1 + i\left(-\frac{\pi}{2} + 2k\pi\right) \]which simplifies to:\[ z = 3 + i\left(-\frac{\pi}{2} + 2k\pi\right) \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Euler's Formula
Euler's Formula is a fundamental bridge between the trigonometric functions and the complex exponential function. It states that for any real number \( x \), \[ e^{ix} = \cos(x) + i\sin(x) \]This remarkable equation allows us to express complex numbers in an exponential form using the angle \( x \) in radians.
- If \( x \) is an angle on the unit circle, \( \cos(x) \) gives the x-coordinate and \( \sin(x) \) gives the y-coordinate, forming the real and imaginary parts of the complex number.
- Euler's formula is especially useful for integrating exponential functions and trigonometric identities.
- In our exercise, Euler's formula helps transform \(-i\) into an exponential form, i.e., \(-i = e^{i(-\frac{\pi}{2})}\), by finding the angle \(-\frac{\pi}{2}\) on the complex plane.
Exponential Equations
Exponential equations involve variables in the exponent. In our original problem, the equation \[ e^{z-1} = -i e^2 \]takes this form, where both sides include exponentials.
- To solve such equations, a common method is to express both sides with the same base. This allows us to equate the exponents directly, simplifying the problem significantly.
- Both real and complex exponential equations have a structure which makes them solveable by transforming all terms into exponential form.
- The solution involves balancing the exponentials by extracting and aligning both the real and imaginary components.
Complex Exponential Form
Complex exponential form is a method of expressing complex numbers as exponentials, particularly useful in solving problems involving rotation and oscillation.
- A complex number \( z \) written as \( z = r e^{i\theta} \) combines the modulus \( r \) with the argument \( \theta \), providing a clear depiction of magnitude and direction.
- This form utilizes Euler's formula and is integral for simplifying complex multiplication and division.
- In our exercise, expressing \(-i\) and other terms in this form allowed us to directly equate exponents, decoupling the problem.
- These transformations lead to straightforward solutions, where previously complex arithmetic becomes a matter of exponent comparison.