You are Here: Home >< Maths

# proof of the differential of sin x Watch

1. (Original post by Plato's Trousers)
actually, yes, I was just re-reading it and wasn't happy with that part.
Remember the law of limits:
2. (Original post by Saichu)
Remember the law of limits:
so do you mean that if we re-write as a product

and take the limits of each in turn, the product of those limits is the limit of the product?

So,

and

the the limit of the product is zero?
3. (Original post by Plato's Trousers)
so do you mean that if we re-write as a product

and take the limits of each in turn, the product of those limits is the limit of the product?

So,

and

the the limit of the product is zero?
that's correct

4. This is the problem line. The statement you need to make for your proof to work is:

You can then cancel the h on top by the h on the bottom. I know it's not a rigorous proof by any means, but it's what makes it work for C3/C4.

It's like:

And

Are equivalent on the limit..

Try for yourself: sin(0.0001) x cos(x) = 0.000099999 cos)x)
5. (Original post by OS92)

This is the problem line. The statement you need to make for your proof to work is:

Nope. His line was fine, it's your line which doesn't make sense.
6. (Original post by OS92)

This is the problem line. The statement you need to make for your proof to work is:

You can then cancel the h on top by the h on the bottom. I know it's not a rigorous proof by any means, but it's what makes it work for C3/C4.

It's like:

And

Are equivalent on the limit..

Try for yourself: sin(0.0001) x cos(x) = 0.000099999 cos)x)
Sorry, but your whole post is nonsense. I don't think you really understand how limits work. In particular, this statement means nothing and is not true:

Once h tends to 0, it can't appear on the RHS.
7. (Original post by SimonM)
Nope. His line was fine, it's your line which doesn't make sense.

(Original post by Swayum)
Sorry, but your whole post is nonsense. I don't think you really understand how limits work. [/latex]
Thanks guys! I was starting to get confused again, having thought I understood it nicely

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 31, 2010
Today on TSR

### Cambridge interview invitations

Has yours come through yet?

### Official Oxford interview invite list

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.