MHB How to Expand cx(x-l) into a Fourier Series?

Click For Summary
The function cx(x-l) is proposed for expansion into a Fourier series of the form Σ a_n e^(-α_n x). There is confusion regarding the term α, with suggestions that it should depend on n for proper Fourier series representation. The discussion indicates that cx(x-l) can be transformed into a series involving complex exponentials. A specific example is provided, showing a potential expansion with constants and exponential terms. The conversation highlights the need for clarity in defining parameters for accurate series representation.
Another1
Messages
39
Reaction score
0
I have a function $$cx(x-l)$$ where c is constant

I want to expansion this function $$cx(x-l)$$ to $$\sum_{n=-\infty}^{\infty}a_{n}e^{-\alpha x}$$

how can i do it? you have a idea
 
Last edited:
Mathematics news on Phys.org
Is there perhaps a typo in the summand? The exponential does not seem to depend on $n$ and it is not clear to me what $\alpha$ is.
 
Janssens said:
Is there perhaps a typo in the summand? The exponential does not seem to depend on $n$ and it is not clear to me what $\alpha$ is.


$$cx(x-l)$$ to $$\sum_{n=-\infty}^{\infty}a_{n}e^{-\alpha_{n} x}$$ $\alpha$ is constant any constant
 
Another said:
$$cx(x-l)$$ to $$\sum_{n=-\infty}^{\infty}a_{n}e^{-\alpha_{n} x}$$ $\alpha$ is constant any constant

That looks like a Fourier series transform.

We have:
$$cx(x-1) = c\left(\frac{\pi^2}3 + (-2-i)e^{-ix} - (2-i)e^{ix} + ...\right)$$
 
Thread 'erroneously  finding discrepancy in transpose rule'
Obviously, there is something elementary I am missing here. To form the transpose of a matrix, one exchanges rows and columns, so the transpose of a scalar, considered as (or isomorphic to) a one-entry matrix, should stay the same, including if the scalar is a complex number. On the other hand, in the isomorphism between the complex plane and the real plane, a complex number a+bi corresponds to a matrix in the real plane; taking the transpose we get which then corresponds to a-bi...

Similar threads

  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 33 ·
2
Replies
33
Views
3K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 17 ·
Replies
17
Views
1K
  • · Replies 7 ·
Replies
7
Views
2K