Turn on thread page Beta
 You are Here: Home >< Maths

# Fourier series,Help! watch

1. Would anyone help me to do the following question? Thanks
Attached Images

2. Which module is this from?
3. (Original post by superkillball)
Would anyone help me to do the following question? Thanks
Its late check so please check for any silly errors.
f(x)=-1 if -L<x<0
f(x)=1 if 0<x<L
since f(-x)=-f(x) f is odd => a0 and an=0 for all n
piBn=int from {-L<x<0} of {-sin(nx)}dx+{0 to L} {sin(nx)}dx
piBn={1/ncos(nx)}at x=-L and x=0 + {-1/ncos(nx)} at x=0 to x=L
piBn=[1/n-{1/ncos(nl)}]+[-{1/ncos(nl)}-{-1/n}]
Bn=2{1-cosnl}/npi
when L=pi
Bn=2{1-cos(pi n)}/npi
so
Bn=0 n even
=4/pi n odd
so
f(x)=4/pi{(sinx)+(sin3x)/3+(sin5x)/5+...
4. (Original post by evariste)
Its late check so please check for any silly errors.
f(x)=-1 if -L<x<0
f(x)=1 if 0<x<L
since f(-x)=-f(x) f is odd => a0 and an=0 for all n
piBn=int from {-L<x<0} of {-sin(nx)}dx+{0 to L} {sin(nx)}dx
piBn={1/ncos(nx)}at x=-L and x=0 + {-1/ncos(nx)} at x=0 to x=L
piBn=[1/n-{1/ncos(nl)}]+[-{1/ncos(nl)}-{-1/n}]
Bn=2{1-cosnl}/npi
when L=pi
Bn=2{1-cos(pi n)}/npi
so
Bn=0 n even
=4/pi n odd
so
f(x)=4/pi{(sinx)+(sin3x)/3+(sin5x)/5+...
thanks

Turn on thread page Beta
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: January 22, 2005
Today on TSR

### Cambridge interviews

Find out who is getting invitations

### University open days

• Heriot-Watt University
School of Textiles and Design Undergraduate
Fri, 16 Nov '18
• University of Roehampton
Sat, 17 Nov '18
• Edge Hill University
Faculty of Health and Social Care Undergraduate
Sat, 17 Nov '18
Poll
Useful resources

## Make your revision easier

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams

Can you help? Study help unanswered threads

## Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE