Turn on thread page Beta
    • Thread Starter
    Offline

    13
    ReputationRep:
    in this paper https://madasmaths.com/archive/iygb_...apers/c4_d.pdf
    question 5 b you need to make the gradient 0 which i understand as thats the maximum point of the circle however the mark scheme says that you must also make dy/dx equal to infinity which i do not understand how on earth could a gradient be forever big and small?
    https://madasmaths.com/archive/iygb_..._solutions.pdf
    those are the solutions.
    • Community Assistant
    Offline

    20
    ReputationRep:
    Community Assistant
    (Original post by BubbleBabby)
    in this paper https://madasmaths.com/archive/iygb_...apers/c4_d.pdf
    question 5 b you need to make the gradient 0 which i understand as thats the maximum point of the circle however the mark scheme says that you must also make dy/dx equal to infinity which i do not understand how on earth could a gradient be forever big and small?
    https://madasmaths.com/archive/iygb_..._solutions.pdf
    those are the solutions.
    Infinite gradient is just used to denote the gradient of vertical line. It doesnt really make sense to make it equal infinity as infinity is not a number, but writing dy/dx=infinity gets the notion of infinite steepness across.

    The alternative notation would be to say that dx/dy=0
    • Community Assistant
    Offline

    17
    ReputationRep:
    Community Assistant
    The gradient (dy/dx) is meant as change in y/change in x.

    In a vertical line, the change in y is infinity (it rises from -infinity to infinity) and the change in x is 0 hence the gradient = infinity. But it's not an number.

    Hence dy/dx = infinity but this isn't useful --> take reciprocals of both sides: 1/dy/dx = 1/infinity --> dx/dy = 0.

    In a horizontal line, the change in y is 0 but change in x is infinity therefore the gradient is 0 and dy/dx = 0 but dx/dy = infinity.
    • Thread Starter
    Offline

    13
    ReputationRep:
    (Original post by RDKGames)
    Infinite gradient is just used to denote the gradient of vertical line. It doesnt really make sense to make it equal infinity as infinity is not a number, but writing dy/dx=infinity gets the notion of infinite steepness across.

    The alternative notation would be to say that dx/dy=0
    ooooooooh ok because it's infanitly steep! i get it!!!! Thank you!!!
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: February 23, 2018

University open days

  1. University of Bradford
    University-wide Postgraduate
    Wed, 25 Jul '18
  2. University of Buckingham
    Psychology Taster Tutorial Undergraduate
    Wed, 25 Jul '18
  3. Bournemouth University
    Clearing Campus Visit Undergraduate
    Wed, 1 Aug '18
Poll
How are you feeling in the run-up to Results Day 2018?
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

Equations

How to use LaTex

Writing equations the easy way

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

Thinking about a maths degree?

Chat with other maths applicants

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups

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

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.