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: Second derivative

  1. Nov 16, 2005 #1
    I am Calculus AB student. I know how to find first derivative, second derivative, prove points of inflecition, find concavity...but as I just finnished the last section of chapter 4 and chapter 5 is Integrals, I still have one question that remains unanswered: Why is it important to find concavity? I know that f"(x) lets you find accelelration fro distance, and Jerk from speed, but why do I care that a function is concave up from (-inf, -2) Reunited with (4, inf) ? is it going to make any application that will be needed for? Everything I studied so far made mo reference to concavity.

    Critical points that give the mins and maxes in first derivative...those are useful. but my question stays: What is concavity and Inflection points important for?
  2. jcsd
  3. Nov 17, 2005 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    After you find the mins and maxs with the first derivitive, you use the 2nd derivitive (concavity) to determine if a point is a max or a min. Concave up implies a max, concave down implies a min.
  4. Nov 17, 2005 #3
    Don't you do that by looking at the sign changes in f'(x) and if it comes from - to + it's a min, and from + to - it's a max? That's how I learned it.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook