Results 1 to 3 of 3

Math Help - Tangent & Normal (Q8b)

  1. #1
    Super Member
    Joined
    Dec 2009
    Posts
    755

    Tangent & Normal (Q8b)

    The tangent and the normal to the curve y=4(\sqrt{x+2}) at the point P(7,12) cut the x-axis at point M and N respectively. Calculate the area of the Triangle PMN.

    I am aware that I have to find the equation of the tangent and the normal. However, I seem to not be able to get them correctly... The problem lies with getting the equation of the tangent and normal. Calculating the area of the triangle should be fine, so I require no help in it.

    I would be grateful if someone would show me the detailed workings on getting the equations of tangent and normal, thanks!
    Last edited by Punch; February 17th 2010 at 08:14 AM.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Sep 2008
    From
    West Malaysia
    Posts
    1,261
    Quote Originally Posted by Punch View Post
    The tangent and the normal to the curve y=4(\sqrt{x+2}) at the point P(7,12) cut the x-axis at point M and N respectively. Calculate the area of the Triangle PMN.

    I am aware that I have to find the equation of the tangent and the normal. However, I seem to not be able to get them correctly... The problem lies with getting the equation of the tangent and normal. Calculating the area of the triangle should be fine, so I require no help in it.

    I would be grateful if someone would show me the detailed workings on getting the equations of tangent and normal, thanks!
    first of all , differentiate to find the gradient of tangent .

    \frac{dy}{dx}=\frac{2}{\sqrt{x+2}}

    and at (7,12) , \frac{dy}{dx}=\frac{2}{\sqrt{7+2}}=2/3

    equation of tangent : y-12=(2/3)(x-7)

    gradient of normal = -3/2

    equation of normal : y-12=(-3/2)(x-7)
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Super Member
    Joined
    Dec 2009
    Posts
    755
    I think I found the problem now... I didn't sub value of x into the \frac{dy}{dx} thanks!
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. tangent and normal
    Posted in the Calculus Forum
    Replies: 1
    Last Post: March 9th 2011, 08:27 AM
  2. Tangent & Normal(Q6)
    Posted in the Pre-Calculus Forum
    Replies: 6
    Last Post: February 19th 2010, 10:17 PM
  3. Tangent & Normal Q11
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: February 17th 2010, 12:18 PM
  4. Tangent and normal
    Posted in the Calculus Forum
    Replies: 2
    Last Post: September 27th 2009, 11:19 AM
  5. tangent & normal
    Posted in the Geometry Forum
    Replies: 7
    Last Post: January 18th 2009, 04:00 AM

Search Tags


/mathhelpforum @mathhelpforum