What is the solution to the complex cosine equation without using logarithms?

  • Thread starter Thread starter diddy_kaufen
  • Start date Start date
  • Tags Tags
    Complex Cosine
Click For Summary

Homework Help Overview

The discussion revolves around solving the complex equation $$\cos(\pi e^z) = 0$$ without utilizing logarithmic identities. Participants are exploring the implications of the equation and the constraints imposed by the homework guidelines.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants are attempting to manipulate the equation into a form that avoids logarithms, discussing the implications of the real and imaginary parts of the equation. There is uncertainty about how to express certain variables without resorting to logarithmic functions.

Discussion Status

The discussion is ongoing, with participants providing insights and suggestions. Some have proposed substituting variables and examining the real and imaginary components, while others express concern about inadvertently using logarithmic concepts. There is no explicit consensus on the approach to take.

Contextual Notes

Participants are constrained by the requirement to avoid complex logarithm identities, which is influencing their problem-solving strategies and discussions about potential solutions.

diddy_kaufen
Messages
6
Reaction score
0

Homework Statement



Solve the equation

$$cos(\pi e^z) = 0$$

Homework Equations



I am not allowed to use the complex logarithm identities.

$$ \cos z = \frac{e^{iz}+e^{-iz}}{2} $$

$$e^{i\theta}=\cos\theta+i \sin\theta$$

The Attempt at a Solution



All I've gotten is $$\cos(\pi e^z)=0 \iff \pi e^z = \frac{\pi}{2}+p \pi \iff e^z=\frac{1}{2}+p, p\in Z $$

I have no idea how to solve this without resorting to the logarithm.
 
Physics news on Phys.org
Look at the real part and the fact that the imaginary part is 0.
 
but wouldn't I then still be using the logarithm? Since then I would have to do 1/2+p = exp( ln( 1/2+p ) ) but I'm not getting all solutions, since p is in Z and I'm not allowed to evaluate a complex logarithm?
 
diddy_kaufen said:
but wouldn't I then still be using the logarithm? Since then I would have to do 1/2+p = exp( ln( 1/2+p ) ) but I'm not getting all solutions, since p is in Z and I'm not allowed to evaluate a complex logarithm?
You have equations in the "Relevant equations" section that can be used.
 
Thank you for your help, I'm sorry but I'm still stuck. I used the relevant equations to substitute w = e^(iz)to get w=0 or w=-1, so |w|=e^(-y)=0 or |w|=1, so $$e^{iz}=e^{-y}(\cos x_0 + i \sin x_0)$$ which means that $$ x_0=\pi+n2\pi $$

is this even correct? I'm sorry I'm new to complex numbers
 
Continue your first post using ez = ex+iy = exeiy = ex(cos(y) +i sin(y))
 
Ok I get $$e^x (\cos y + i \sin y) = \frac{1}{2}+p$$ or $$e^x \cos y = \frac{1}{2}+p$$ can I work around this without using the logarithm?
 
diddy_kaufen said:
Ok I get $$e^x (\cos y + i \sin y) = \frac{1}{2}+p$$ or $$e^x \cos y = \frac{1}{2}+p$$ can I work around this without using the logarithm?
Don't forget about equating the imaginary parts.
I didn't check your work, so I will assume it is ok. x is a logarithm, so I don't see how to express it without using a logarithm.
 

Similar threads

Replies
13
Views
2K
Replies
1
Views
1K
Replies
7
Views
3K
Replies
9
Views
2K
Replies
3
Views
2K
  • · Replies 14 ·
Replies
14
Views
2K
  • · Replies 11 ·
Replies
11
Views
1K
  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 6 ·
Replies
6
Views
2K