Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Equation of the normal line

  1. Dec 11, 2009 #1
    find the equation of the normal line to the curve y = -3x^2 at the point (-1,-3).

    you have to use derivatives.

    i am not asking for the equation of the tangent line i know that is 6x + 3. please show all the steps.

    the answer is y = -1/6x - 19/6
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Dec 12, 2009 #2


    User Avatar
    Gold Member

    Do you know the relationship between the gradient of two perpendicular lines?
  4. Dec 12, 2009 #3


    Staff: Mentor

    Another term for gradient in this context is "slope." You can use calculus to find the slope of the tangent line. What is the slope of the line perpendicular to the tangent line? That will be the slope of the line you want. You know a point on this line, so you will have all the information you need to get the equation of this second line.
  5. Dec 12, 2009 #4
    thanks i got it
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook