You are Here: Home >< Maths

# taylor series Watch

Announcements
1. I need to expand the funtion cos(z) in taylor series at arbitrary point w belonging to complex numbers. It says to use the addition formula. Z also belongs to complex. So far i hv written out cos(z) = cos(z-w+w) then used addition formula to expand but i'm not sure what to do next, partly because i don't fully understand why i hv to use addition formula, why can't i just use formula for taylor series about a point?
2. (Original post by Ishika)
I need to expand the funtion cos(z) in taylor series at arbitrary point w belonging to complex numbers. It says to use the addition formula. Z also belongs to complex. So far i hv written out cos(z) = cos(z-w+w) then used addition formula to expand but i'm not sure what to do next, partly because i don't fully understand why i hv to use addition formula, why can't i just use formula for taylor series about a point?
Complex analysis, I think I remember having the same question as that. You can't just you the formula around a point simply because cos(z) doesn't equal cos(z-w). Hence you have started right, you just the addition formual to expand and simplify are you are done.
3. After i expand then i hv terms cos(z-w)cozw - sin (z-w)sin(w).
Then do i just expand cos(z-w) using taylor series or maclaurin series?
4. The answer i get is the same as the series expansion for cosz but with z=z-w. Why coudn't i have used the series expansion in the beginning?
5. Could it be that it means writing and using the addition formula on that?
6. There's very little point in doing that - the standard series works just as well for complex z as for real z.

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: December 13, 2010
Today on TSR

### Things NOT to do at uni

Have you done any of these?

### How much revision have yr12s done?

Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Useful resources

### 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

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• 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

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.