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

Equation for the normal to a curve

Announcements Posted on
Become part of the Welcome Squad! Apply here! 28-10-2014
    • Thread Starter
    • 2 followers
    Offline

    ReputationRep:
    A curve has the equation

    x^2+3xy-2y^2+17=0

    Find an expression for dy/dx in terms of x and y. I did this part correctly: dy/dx = (2x+3y)/(4y-3x)

    Find an equation for the normal to the curve at the point (3,-2).
    I got dy/dx = 0, the m of the normal = 0, then the equation of the curve being y=3, but the answer says x=3.
    • 11 followers
    Offline

    ReputationRep:
    gradient of normal is not dy/dx. Thats the gradient of the tangent.
    • 3 followers
    Offline

    ReputationRep:
    Yup. Derivative is the line tangent to the curve, so the 'm' for the normal is dx/dy, or undefined.
    • 66 followers
    Offline

    ReputationRep:
    (Original post by aznkid66)
    Yup. Derivative is the line tangent to the curve, so the 'm' for the normal is dx/dy, or undefined.
    indicting a vertical line through (3,-2)
    • 0 followers
    Offline

    ReputationRep:
    (Original post by TenOfThem)
    indicting a vertical line through (3,-2)
    So grad is infinity
    • 66 followers
    Offline

    ReputationRep:
    (Original post by pwcroberts)
    So grad is infinity
    undefined rather than infinity
    • Thread Starter
    • 2 followers
    Offline

    ReputationRep:
    Oh, ok. Thank you!

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 19, 2012
New on TSR

Halloween 2014

Join the TSR Halloween party...if you dare!

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