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

# C3 Further Integration HELP PLEASE watch

1. I have no idea how to solve the whole of Q7) .

Attached Images

2. well first start by differentiation in part a and lets see where you get
3. (Original post by clad in armour)
well first start by differentiation in part a and lets see where you get
So dy/dx = 2cosX - 1

Eeek... is that correct?
4. (Original post by clad in armour)
well first start by differentiation in part a and lets see where you get
...this

and @OP as you shud prolly know dy/dx gives you the gradient at any point of a curve.Specific Maximum and minimum values are therefore found (in some functions - def in cos and sin fs) when gradient is 0. But remember you'll never kno whther its a max or min til u diff again
5. (Original post by APonderingMind)
So dy/dx = 2cosX - 1

Eeek... is that correct?
yes, and the question asks for the maximum, so you may know as mentioned that dy/dx = o.....
6. (Original post by clad in armour)
yes, and the question asks for the maximum, so you may know as mentioned that dy/dx = o.....
Uh huh, and I did this:

2cosX - 1 = 0
cos X = 1/2
X= 1/3Pi

The answer at the back of my text book says it's root3 - 1/3Pi

So where do I go from here?
7. But y=2sinx -x

Not y = sin2x...
8. (Original post by R3L4Y)
remember it was sin2x ...
It wasn't. It was y=2sinx - 1.
9. (Original post by APonderingMind)
But y=2sinx -x

Not y = sin2x...
hahaha I just realized this thnx
10. (Original post by davidmarsh01)
It wasn't. It was y=2sinx - 1.
it was a test? lol
11. (Original post by APonderingMind)
Uh huh, and I did this:

2cosX - 1 = 0
cos X = 1/2
X= 1/3Pi

The answer at the back of my text book says it's root3 - 1/3Pi

So where do I go from here?
your not finished yet, now you know there is a stationary point at x= 1/3pi, the question asks about the maximum, differentiate again
12. (Original post by clad in armour)
your not finished yet, now you know there is a stationary point at x= 1/3pi, the question asks about the maximum, differentiate again
Second derivative: -2sinX

OOh...yay! I found the answer now.

Subbed 1/3Pi into second derivative to find that it = -root3. This means it is the maximum value.

So then I subbed it into the curve and got the answer root3 - 1/3Pi. =D

Thanks for forcing me to do my own maths question, it actually helped!
13. (Original post by APonderingMind)
Second derivative: -2sinX

OOh...yay! I found the answer now.

Subbed 1/3Pi into second derivative to find that it = -root3. This means it is the maximum value.

So then I subbed it into the curve and got the answer root3 - 1/3Pi. =D

Thanks for forcing me to do my own maths question, it actually helped!
glad to help, you know how to do the other parts?
14. (Original post by clad in armour)
glad to help, you know how to do the other parts?
Yes I can do the other parts thanks =)
15. (Original post by APonderingMind)
Yes I can do the other parts thanks =)
cool

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 11, 2010
Today on TSR

### Negatives of studying at Oxbridge

What are the downsides?

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