1. Not finding help here? Sign up for a free 30min 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!

Find an equation of the line tangent

  1. Sep 6, 2007 #1
    1. The problem statement, all variables and given/known data

    f(x) = |sinx| for - π ≤ x ≤ π
    g(x) = x^2
    h(x)= g(f(x))

    1. Find domain and range of h(x)
    2. Find an equation of the line tangent to the graph of h at the point where x= π/4


    2. Relevant equations



    3. The attempt at a solution

    It think that h(x) is (|sin x|)^2

    so, is domain - π ≤ x ≤ π

    here is where I am confused:

    if d/dx (sin x) = cos x

    then

    is d/dx (|sin x|)^2 = (|cos x|)^2 ?

    thanks in advance for the help.
     
  2. jcsd
  3. Sep 6, 2007 #2

    danago

    User Avatar
    Gold Member


    You cant do that. You should consider using the chain rule.
     
  4. Sep 6, 2007 #3
    is there any rule for the derivate for an absolute value?
     
  5. Sep 6, 2007 #4

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    Squaring makes it easy to answer. |f(x)|^2=f(x)^2. Otherwise you have to split it into subdomains where f(x)>=0 and f(x)<0.
     
  6. Sep 7, 2007 #5

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    |x|= x if [itex]x\ge 0[/itex], -x is x< 0. Its derivative is 1 if x> 0, -1 if x< 0, not defined for x=0.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Find an equation of the line tangent
Loading...