Results are out! Find what you need...fast. Get quick advice or join the chat
Hey! Sign in to get help with your study questionsNew here? Join for free to post

OCR C4 June 11: Vectors and Integration

Announcements Posted on
Applying to Uni? Let Universities come to you. Click here to get your perfect place 20-10-2014
    • Thread Starter
    • 1 follower
    Offline

    ReputationRep:
    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?
    and the mark scheme: http://pdf.ocr.org.uk/download/ms_11...u4724_jun.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.

    Thanks in advance.
    • 2 followers
    Offline

    ReputationRep:
    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.
    • 0 followers
    Offline

    ReputationRep:
    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)

Reply

Submit reply

Register

Thanks for posting! You just need to create an account in order to submit the post
  1. this can't be left blank
    that username has been taken, please choose another Forgotten your password?
  2. this can't be left blank
    this email is already registered. Forgotten your password?
  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
    your full birthday is required
  1. By joining you agree to our Ts and Cs, privacy policy and site rules

  2. Slide to join now Processing…

Updated: June 20, 2012
New on TSR

Submitting your UCAS application

How long did it take for yours to be processed?

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