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

In summary, the student is trying to solve an equation for cosine, but they can't do it without using the logarithm. They are also having trouble getting all the solutions because p is in their complex number domain. They are solving for x using cos y+i sin y, but they should also equate the imaginary parts.
  • #1
diddy_kaufen
7
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
  • #2
Look at the real part and the fact that the imaginary part is 0.
 
  • #3
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?
 
  • #4
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.
 
  • #5
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
 
  • #6
Continue your first post using ez = ex+iy = exeiy = ex(cos(y) +i sin(y))
 
  • #7
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?
 
  • #8
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.
 

1. What is a complex cosine equation?

A complex cosine equation is a mathematical expression that involves both a real and imaginary component in the form of cosine functions. It is used to model complex oscillations and is commonly seen in fields such as physics, engineering, and mathematics.

2. How do you solve a complex cosine equation?

To solve a complex cosine equation, the first step is to separate the real and imaginary parts of the equation. Then, use trigonometric identities to simplify each part. Finally, use algebraic techniques to solve for the unknown variable.

3. What are some real-life applications of complex cosine equations?

Complex cosine equations can be used to model a variety of natural phenomena such as sound waves, electromagnetic waves, and electrical circuits. They are also used in signal processing and data analysis to extract information from complex signals.

4. Can a complex cosine equation have multiple solutions?

Yes, a complex cosine equation can have multiple solutions. This is due to the periodic nature of cosine functions, which means that the equation can have an infinite number of solutions that repeat at regular intervals.

5. What is the difference between a complex cosine equation and a real cosine equation?

The main difference between a complex cosine equation and a real cosine equation is that the former involves both real and imaginary components, while the latter only involves real components. Additionally, complex cosine equations have a more general form and can be used to model more complex oscillations compared to real cosine equations.

Similar threads

  • Calculus and Beyond Homework Help
Replies
1
Views
290
  • Calculus and Beyond Homework Help
Replies
13
Views
1K
  • Calculus and Beyond Homework Help
Replies
3
Views
565
  • Calculus and Beyond Homework Help
Replies
11
Views
367
  • Calculus and Beyond Homework Help
Replies
7
Views
1K
  • Calculus and Beyond Homework Help
Replies
3
Views
421
  • Calculus and Beyond Homework Help
Replies
2
Views
508
  • Calculus and Beyond Homework Help
Replies
4
Views
142
  • Calculus and Beyond Homework Help
Replies
1
Views
540
  • Calculus and Beyond Homework Help
Replies
9
Views
2K
Back
Top