1. Limited time only! Sign up for a free 30min personal 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!

Primitive Function 3(sin(3t) + cos(3t))

  1. May 26, 2014 #1
    1. The problem statement, all variables and given/known data
    Find the primitive function s(t) for v(t)=3(sin(3t) + cos(3t)) for which s(0)=0


    3. The attempt at a solution

    v(t) =3(sin(3t) + cos(3t)) = 3sin3t +3cos3t

    s(t) =cos3t -sin3t + C

    0 = cos3(0) - sin3(0) + C
    0= 1 + C
    C=-1
    such that my primitive function is cos3t - sin3t - 1

    My teacher got another answer:
    s(t) = -cos(3t) + sin(3t) + C
    and s(0) = 0 = -1 + 0 + C such that C= 1 and the primitive function is sin3t -cos3t + 1

    has he made a mistake? or am I confused?
     
  2. jcsd
  3. May 26, 2014 #2
    You've made mistakes. What is the primitive function of cos and sin?
     
  4. May 26, 2014 #3
    the primitive function is the anti-derivative. so cosx becomes sinx and sinx becomes -cosx?
    s(t)=-cos3t+sin3t + C

    Now I got it. I´d gotten confused between the derivative and the anti-derivative. Thanks for confirming that I´d made the mistake!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Primitive Function 3(sin(3t) + cos(3t))
  1. Primitive sin (x^3) (Replies: 13)

Loading...