1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
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: Triangle formed by tangents to parabola.

  1. Dec 10, 2015 #1
    1. The problem statement, all variables and given/known data
    The triangle formed by the tangents to the parabola y2=4ax, at the ends of the latus rectum and the double ordinate through it's focus is:
    1) equilateral 2) acute angles isosceles 3)right angled isosceles 4) dependent on value of a

    2. Relevant equations

    3. The attempt at a solution
    The double ordinate through the focus is the latus rectum. I tried to find the intersection of the two tangents by using the AM and GM of the co-ordinates of the points of contact with the parabola .
    the two points of contact : (a,2a) and (a,-2a)
    x-coordinate of intersection = GM=√a2=a
    y-coordinate of intersection = AM= 2a-2a/2 =0
    Which gives me the intersection of the two tangents to be (a,0) which is the co-ordinates of the focus. This is clearly wrong. Where am I going wrong in my approach?
  2. jcsd
  3. Dec 10, 2015 #2


    User Avatar
    Science Advisor
    Homework Helper

    Maybe you should post how you compute(d) the slope of the tangents at the two points of contact.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted