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Bounded derivative

  1. Apr 15, 2009 #1
    Hi all, my first post so go easy on me! Doing some revision and have been tripped up on a really simple question!

    Where f(x) = xCos(x)

    Show the bound f '(x)<=6 is valid for 0<= x<=5

    I suspect this is an easy solution using the intermediate value theorem!

    Thanks in advance,

  2. jcsd
  3. Apr 15, 2009 #2
    f'(x) = cos(x) + x*sin(x) <= 1 + 5*1 = 6
  4. Apr 15, 2009 #3
    Ahhh, something just moved in my brain...

    Thanks very much! :D
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