Results 1 to 3 of 3

Math Help - derivative of sinx/6

  1. #1
    Junior Member
    Joined
    Oct 2008
    Posts
    34

    derivative of sinx/6

    if F(x) = sin^5 (x/6) + cos^4 (x/3)
    find F'(x)

    I'm doing the wrong derivative, i thought that the derivative of
    sin(x/6) = cos (x/6)
    but that doesn't seem to be correct.

    Let's say we're looking at
    (sin(x/6))^5 ( i took the 5 out for chain rule purposes)

    then
    5(sin(x/6))^4 is the derivative of the outside applied to the inside,
    and the derivative of the inside(sin(x/6)) is x/6 * (cos(x/6))??

    i thought that the derivative would be

    5(sin(x/6))^4 * (cos(x/6))

    is there a rule for the x/6 to come out of there?

    I can solve the problem, i just need to figure out if i'm missing something specifically with the derivative.
    i can't exactly keep going if the derivative is wrong
    thanks a bunch
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Junior Member
    Joined
    Mar 2009
    Posts
    53
    just think of it like this:

    d/dx of sin(u) = u' cos(u)

    d/dx sin(x) = 1(cos(x))

    d/dx sin(4x) = 4(cos(4x))

    d/dx sin(x/6) [or, sin((1/6)x)] = (1/6)(cos(x/6))
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor
    Joined
    Oct 2008
    Posts
    1,035
    Thanks
    49
    And, just in case a picture helps...





    Don't integrate - balloontegrate!

    Balloon Calculus: worked examples from past papers
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. ((1+sinx+icosx)/(1+sinx-icos))^n
    Posted in the Trigonometry Forum
    Replies: 5
    Last Post: November 28th 2011, 07:06 PM
  2. Replies: 1
    Last Post: March 25th 2011, 12:27 AM
  3. Replies: 1
    Last Post: May 31st 2010, 04:29 PM
  4. derivative of sinx/tan3x
    Posted in the Calculus Forum
    Replies: 2
    Last Post: March 7th 2010, 03:04 PM
  5. The second derivative of Y= x(Sinx)
    Posted in the Calculus Forum
    Replies: 2
    Last Post: June 20th 2009, 02:17 PM

Search Tags


/mathhelpforum @mathhelpforum