# Fourier Series finding An term

Hi,

Here is my working for finding A_n given knowledge that the sum is equal to a constant, l is a constant so the sinh(nl) part is just constant, my answer is mostly correct except it is 2 rather than 4 but I’ve gone over it so much and can’t find where the 4 comes from? Maybe where I am integrating but I’ve triple checked

It might seem stupid to ask about a mistake but small mistakes like this might be me actually misunderstandings part of the process

Do you have the original question?
Original post by mqb2766
Do you have the original question?

This is the original question, but I am just worried about the last boundary condition phi(x,l)= phi_0
Original post by mqb2766
Do you have the original question?

Sorry I meant to send this
Original post by mqb2766
Do you have the original question?

Actually never mind, I believe the problem is that x > 0 in the question but I am integrating over [pi, -pi]
Original post by grhas98
This is the original question, but I am just worried about the last boundary condition phi(x,l)= phi_0

Original post by grhas98

Sorry I meant to send th

Original post by grhas98
Actually never mind, I believe the problem is that x > 0 in the question but I am integrating over [pi, -pi]

Sounds reasonable, but not checked.
Original post by grhas98
Actually never mind, I believe the problem is that x > 0 in the question but I am integrating over [pi, -pi]

Also the lhs looked like it was 0 not 2 when its was -pi .. pi.
Original post by mqb2766
Sounds reasonable, but not checked.

Oh yeah, ty