Page 1 of 2 12 LastLast
Results 1 to 15 of 23
Like Tree15Thanks

Math Help - Differentiate the functions.

  1. #1
    Junior Member
    Joined
    Sep 2012
    From
    NYC
    Posts
    37

    Differentiate the functions.

    I was absent for the first time in my math class due to an emergency and now I'm falling behind everyone else in the class. I really need some help differentiating these functions. Please help me!


    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor MarkFL's Avatar
    Joined
    Dec 2011
    From
    St. Augustine, FL.
    Posts
    1,988
    Thanks
    734

    Re: Differentiate the functions.

    Let's take these one at a time. First, it would be helpful to know what your thoughts are on how to differentiate the function in part a). Do you know the power rule? Do you know how to differentiate trigonometric functions?
    Thanks from calculus123
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Sep 2012
    From
    NYC
    Posts
    37

    Re: Differentiate the functions.

    The power rule is
    How would I use this to solve a)?

    Thanks Man!
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie
    Joined
    Oct 2012
    From
    Maryland
    Posts
    22
    Thanks
    4

    Re: Differentiate the functions.

    These problems are all just straight definitions. Use the power rule to do 2x^4 and -x^-4. Sec x and cos x are identities. There should be a table in your book.
    Thanks from calculus123
    Follow Math Help Forum on Facebook and Google+

  5. #5
    MHF Contributor MarkFL's Avatar
    Joined
    Dec 2011
    From
    St. Augustine, FL.
    Posts
    1,988
    Thanks
    734

    Re: Differentiate the functions.

    You can apply the power rule to the first and last terms. Do you know what the derivatives of the secant and cosine functions are?
    Thanks from calculus123
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Junior Member
    Joined
    Sep 2012
    From
    NYC
    Posts
    37

    Re: Differentiate the functions.

    The derivatives of the secant and cosine are SecXTanX and -Sinx, correct? I'm still very confused about approaching this problem. This might seem easy to you guys because you are all math geniuses here but I have a hard time with math in general.
    Follow Math Help Forum on Facebook and Google+

  7. #7
    MHF Contributor MarkFL's Avatar
    Joined
    Dec 2011
    From
    St. Augustine, FL.
    Posts
    1,988
    Thanks
    734

    Re: Differentiate the functions.

    Hey, we were all students once, we all had to learn, and you are doing fine. You have correctly given the power rule, and the rules for the two trig. functions involved, so now you just need to put it all together, term by term. What is your result?
    Thanks from calculus123
    Follow Math Help Forum on Facebook and Google+

  8. #8
    Newbie
    Joined
    Oct 2012
    From
    Maryland
    Posts
    22
    Thanks
    4

    Re: Differentiate the functions.

    You need to work the problems step by step.

    Let's start with a.

    We can take the derivative of each individual portion.

    f'(x) = (2x^4)' + (5sec(x))' - (3cos(x))' - (x^-4)'
    Power rule: (2x^4)' = 8x^3
    Secant Function: (5sec(x))' = 5sec(x)tan(x)
    Cosine Function: (3cos(x))' = -3sin(x)
    Power rule: (x^-4)' = -4x^-5

    Now, sub back into the formula.
    f'(x) = 6x^3 + 5sec(x)tan(x) + 3sin(x) + 4x^-5

    If you are having trouble with the individual portions, that is mostly a memorization task. Just study the properties of derivatives.

    Don't feel dumb. Really, everyone had to learn this at some point. It wasn't easy at first.
    Last edited by wtrmlncrawl191; October 8th 2012 at 07:53 PM.
    Thanks from calculus123
    Follow Math Help Forum on Facebook and Google+

  9. #9
    MHF Contributor MarkFL's Avatar
    Joined
    Dec 2011
    From
    St. Augustine, FL.
    Posts
    1,988
    Thanks
    734

    Re: Differentiate the functions.

    Quote Originally Posted by wtrmlncrawl191 View Post
    ...
    Power rule: (2x^4)' = 6x^3...
    You want:

    \frac{d}{dx}(2x^4)=8x^3
    Thanks from calculus123
    Follow Math Help Forum on Facebook and Google+

  10. #10
    Newbie
    Joined
    Oct 2012
    From
    Maryland
    Posts
    22
    Thanks
    4

    Re: Differentiate the functions.

    Guess I better stop giving advice past 10 pm...Oops. :/
    Thanks from calculus123
    Follow Math Help Forum on Facebook and Google+

  11. #11
    Junior Member alane1994's Avatar
    Joined
    Oct 2012
    From
    Iowa, United States
    Posts
    65
    Thanks
    8

    Re: Differentiate the functions.

    Quote Originally Posted by wtrmlncrawl191 View Post
    Guess I better stop giving advice past 10 pm...Oops. :/
    I am like that too, once it reaches a certain time of night, I am done.
    Also, if you want a reference page try this one calculus. Mathwords: Derivative Rules
    It has all of the basic rules on it, it is very helpful.
    Thanks from calculus123
    Follow Math Help Forum on Facebook and Google+

  12. #12
    Junior Member
    Joined
    Sep 2012
    From
    NYC
    Posts
    37

    Re: Differentiate the functions.

    Are these two correct?
    Follow Math Help Forum on Facebook and Google+

  13. #13
    MHF Contributor MarkFL's Avatar
    Joined
    Dec 2011
    From
    St. Augustine, FL.
    Posts
    1,988
    Thanks
    734

    Re: Differentiate the functions.

    All but the first term in part b) are correct.
    Thanks from calculus123
    Follow Math Help Forum on Facebook and Google+

  14. #14
    Junior Member
    Joined
    Sep 2012
    From
    NYC
    Posts
    37

    Re: Differentiate the functions.

    You mean the 1/3x^2 ? I don't understand why it's wrong.
    Follow Math Help Forum on Facebook and Google+

  15. #15
    Newbie
    Joined
    Oct 2012
    From
    Maryland
    Posts
    22
    Thanks
    4

    Re: Differentiate the functions.

    Remember that 1/x^3 is the same as x^(-3). Then apply the power rule. The coefficient -3 goes on top, and the x^4 goes on the bottom.
    Thanks from calculus123
    Follow Math Help Forum on Facebook and Google+

Page 1 of 2 12 LastLast

Similar Math Help Forum Discussions

  1. how to differentiate this
    Posted in the Calculus Forum
    Replies: 1
    Last Post: December 8th 2011, 07:56 PM
  2. Differentiate the given functions.
    Posted in the Calculus Forum
    Replies: 8
    Last Post: October 22nd 2011, 06:32 PM
  3. Differentiate trig functions
    Posted in the Calculus Forum
    Replies: 2
    Last Post: February 24th 2011, 07:49 AM
  4. Help with differentiate functions
    Posted in the Calculus Forum
    Replies: 2
    Last Post: February 8th 2010, 08:49 PM
  5. Differentiate functions
    Posted in the Calculus Forum
    Replies: 2
    Last Post: April 12th 2006, 02:31 PM

Search Tags


/mathhelpforum @mathhelpforum