Results 1 to 9 of 9

Math Help - Finding normal and tangent to a curve.

  1. #1
    Junior Member
    Joined
    Oct 2010
    Posts
    63

    Finding normal and tangent to a curve.

    Hey im doing exam revision and new to this site, the question im stuck on is this"

    Find the equation of the tangent and normal for:
    f(x)=2x^2-3x+4 at points (3,13)


    thanks
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor Unknown008's Avatar
    Joined
    May 2010
    From
    Mauritius
    Posts
    1,260
    Differentiate the curve.

    Put in x = 3.

    This gives your the gradient of the tangent.

    Now, find the gradient of the normal so that: gradient of tangent x gradient of normal = -1

    You have a point, and a gradient for the tangent line,
    a point and a gradient of the normal line.

    This should not be too difficult.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Oct 2010
    Posts
    63
    yeah ive attemped the question and cant get it right im not sure what im doing wrong. can someone please answear it with working out, it will be a huge help
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor Unknown008's Avatar
    Joined
    May 2010
    From
    Mauritius
    Posts
    1,260
    The derivative is:

    f'(x) = ....

    The gradient of tangent at x = 3 is:

    f'(3) = ....

    Gradient of normal is then -1/f'(3) = ....

    Equation of tangent : y - y1 = f'(3)(x - x1): .....

    Equation of normal: y - y1 = (-1/f'(3)) (x - x1) : .....


    Moderator edited so that the OP does some work of his/her own
    Last edited by mr fantastic; November 9th 2010 at 03:09 AM.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by iFuuZe View Post
    yeah ive attemped the question and cant get it right im not sure what im doing wrong. can someone please answear it with working out, it will be a huge help
    How it works is that you show all your working so that what you're doing wrong can be pointed out to you. Not the other way around.
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Junior Member
    Joined
    Oct 2010
    Posts
    63
    ok i got 4x-3
    i put 3 in the rule and got 12-3=9
    thats all i can think of
    Follow Math Help Forum on Facebook and Google+

  7. #7
    MHF Contributor

    Joined
    Apr 2005
    Posts
    14,973
    Thanks
    1121
    What is the equation of the line through the point (a, b) with slope m?
    Follow Math Help Forum on Facebook and Google+

  8. #8
    MHF Contributor Unknown008's Avatar
    Joined
    May 2010
    From
    Mauritius
    Posts
    1,260
    Yes, do you know what you just got?
    Follow Math Help Forum on Facebook and Google+

  9. #9
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by iFuuZe View Post
    ok i got 4x-3
    i put 3 in the rule and got 12-3=9
    thats all i can think of
    Yes, f'(3) = 9. Now continue, using post #4 as a guide (you did read post #4, right?)
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 3
    Last Post: December 29th 2009, 04:02 PM
  2. Replies: 1
    Last Post: November 12th 2009, 01:35 PM
  3. Finding normal and tangent of a curve
    Posted in the Calculus Forum
    Replies: 1
    Last Post: October 14th 2009, 03:50 PM
  4. Replies: 4
    Last Post: March 23rd 2008, 10:07 PM
  5. Equations of tangent and normal to a curve
    Posted in the Calculus Forum
    Replies: 1
    Last Post: January 7th 2008, 05:04 PM

Search Tags


/mathhelpforum @mathhelpforum