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: Limit value using definition of derivative

  1. Nov 1, 2011 #1
    1. The problem statement, all variables and given/known data
    I have encountered a limit that I wasn't really sure whether I was solving right, it's limit (a). I thought that I could find it considering a function f(x) (b) , find the derivative of that function and substitute x->1 so that I can find the value of the limit. Is this correct thinking???


    2. Relevant equations

    (a) lim(x->1) [ sin(x*pi/4) - sin(pi/4) ] / x-1

    (b) f(x) = sin(x *pi/4) and so f ' (x) = pi/4 cos(x* pi/4)


    3. The attempt at a solution
    That would mean that (a) = f ' (1) = pi/4 * (√2)/2 , right?
     
  2. jcsd
  3. Nov 1, 2011 #2

    lurflurf

    User Avatar
    Homework Helper

    yes that is right
     
  4. Nov 1, 2011 #3
    Ok, excellent, thanks!
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook