Results are out! Find what you need...fast. Get quick advice or join the chat
x

Unlock these great extras with your FREE membership

  • One-on-one advice about results day and Clearing
  • Free access to our personal statement wizard
  • Customise TSR to suit how you want to use it

C1 circles help

Announcements Posted on
Rate your uni — help us build a league table based on real student views 19-08-2015
  1. Offline

    ReputationRep:
    I don't understand the very last part to these questions, 'Find the values of k for which the line is a tangent to the circle'.

    I've worked out that k = -3/4 and k = 4/3.. if i put these into the line equation I get Y = -3/4x + 6 and y = 4/3X + 6.. how do I know these lines are tangents to the circle?

    Click image for larger version. 

Name:	k.JPG 
Views:	55 
Size:	49.1 KB 
ID:	147020
  2. Offline

    ReputationRep:
    (Original post by tom472)
    I don't understand the very last part to these questions, 'Find the values of k for which the line is a tangent to the circle'.

    I've worked out that k = -3/4 and k = 4/3.. if i put these into the line equation I get Y = -3/4x + 6 and y = 4/3X + 6.. how do I know these lines are tangents to the circle?

    Click image for larger version. 

Name:	k.JPG 
Views:	55 
Size:	49.1 KB 
ID:	147020
    You've found the equation for where they intersect. And then you've found an equation in k when these have 1 repeated root. Do you remember what one repeated root means?


    Say if I gave you a regular quadratic with 1 repeated root (b^2 - 4ac = 0) how would you describe what that graph looks like?
  3. Offline

    ReputationRep:
    If it had one repeated root does that mean it touches the x axis once? Sorry I still don't get how I know theyre tangents
  4. Offline

    ReputationRep:
    (Original post by tom472)
    If it had one repeated root does that mean it touches the x axis once? Sorry I still don't get how I know theyre tangents
    Yep that's right. So if we've made this straight line and this circle equal (by subbing in for y like you did) and they only have one repeated root then the same thing applies; the line only 'touches' the circle i.e. it's a tangent.
  5. Offline

    ReputationRep:
    (Original post by hassi94)
    Yep that's right. So if we've made this straight line and this circle equal (by subbing in for y like you did) and they only have one repeated root then the same thing applies; the line only 'touches' the circle i.e. it's a tangent.
    How do you do 7)d)i?
  6. Offline

    ReputationRep:
    (Original post by GreenLantern1)
    How do you do 7)d)i?
    sub y = kx + 6 into the equation of the circle, expand and simplify.
  7. Offline

    ReputationRep:
    (Original post by hassi94)
    sub y = kx + 6 into the equation of the circle, expand and simplify.
    Ahh I see know, cheers

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: May 11, 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.

Today on TSR

Win a mini-fridge

Don't miss our Freshers competition!

Poll
Do you prefer exams or coursework?
Study resources
Quick reply
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.