Results are out! Find what you need...fast. Get quick advice or join the chat
Hey there Sign in to join this conversationNew here? Join for free

Circles and gradients

Announcements Posted on
Got a question about Student Finance? Ask the experts this week on TSR! 14-09-2014
    • Thread Starter
    • 0 followers
    Offline

    ReputationRep:
    http://www.thomas-reddington.com/upl...p_jan_2009.pdf

    For question 5a)

    In the mark scheme they are finding the gradeints for PQ and QR, then multiplying them, I have no idea why?
    • 0 followers
    Offline

    ReputationRep:
    Find the gradient of PQ, find the perpendicular for the gradient of QR, find the equation of QR, substitute the y value for a.

    You should be familiar with m1m2 = -1, another way of finding the perpendicular gradient.
    • 0 followers
    Offline

    ReputationRep:
    theyre perpandicular (because the triangle inside a semicircle is right angled) and hence the product of their gradients is -1.
    So from this it should be easy to work out your value for a
    • Thread Starter
    • 0 followers
    Offline

    ReputationRep:
    (Original post by Joshmeid)
    Find the gradient of PQ, find the perpendicular for the gradient of QR, find the equation of QR, substitute the y value for a.

    You should be familiar with m1m2 = -1, another way of finding the perpendicular gradient.
    This is the first time i've seen of m1m2 = -1.
    • 0 followers
    Offline

    ReputationRep:
    (Original post by zoxe)
    This is the first time i've seen of m1m2 = -1.
    m1 is the gradient of PQ.

    Lets say PQ = 5 for example.

    we have m1m2 = -1

    We now substitute m1 = 5

    5m2 = -1

    m2 = -1/5
    • Thread Starter
    • 0 followers
    Offline

    ReputationRep:
    ive solved it with Pythagoras, however i'm still baffled on how theyve done it
    • Thread Starter
    • 0 followers
    Offline

    ReputationRep:
    (Original post by Joshmeid)
    m1 is the gradient of PQ.

    Lets say PQ = 5 for example.

    we have m1m2 = -1

    We now substitute m1 = 5

    5m2 = -1

    m2 = -1/5
    Why does PQ = gradient?

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: April 17, 2012
New on TSR

Writing your personal statement

Our free PS builder tool makes it easy

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