You are Here: Home

# OCR C4 June 11: Vectors and Integration

Announcements Posted on
Take our survey to be in with the chance of winning a £50 Amazon voucher or one of 5 x £10 Amazon vouchers 28-05-2016
1. I've just done a past paper and I'm struggling on a couple of questions. Here's the question paper: http://pdf.ocr.org.uk/download/pp_11..._gce_4724.pdf?

2) I understand that the modulus of the vector is 5, but I don't understand what the next bit (they multiplied the vector by 1/5), can someone please explain this?

3)ii) The only part of this that I don't understand is how x/((x^2)+3) integrates to .5ln((x^2)+3). Can someone please explain this.

2. 2) You multiply it by 1/5 to get a modulus of 1 as the modulus of the unit vector is 1.

3. ii) You use the f'(x)/f(x) rule. But, you need to tweak the numerator so you get 2x, which is then the differential of the denominator, but to account for the change, you multiple it by .5.
3. 2) The unit vector is the vector given divided by its magnitude. That is how it is defined. So to find the unit vector you find the magnitude of the given vector, in this case 5 and then divide each component in the vector by it.

3)ii)
For this you use the derivative over a function rule. The top of the fraction is x, the derivative of the bottom is 2x.

So pull out of a half (or you could say multiply the top by 2 and bring out a half in front) to get (1/2) X 2x/(x^2+3).

This integrates to 1/2 ln(x^2+3)

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. Oops, you need to agree to our Ts&Cs to register

Updated: June 20, 2012
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:
Today on TSR

### Don't be a half-term hermit

How to revise this week and still have a life

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read here first

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams