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Math Help - unit tangent vector plz

  1. #1
    Newbie
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    unit tangent vector plz

    hi every one i need help

    Find the unit tangent vector at the indicated point of the vector
    function
    r
    (t) = e^15t cost i+e^15t sint j+e^15t k

    T
    (pi/2) =
    i compute the r'(t) = (-e^15tsint+15e^15tcost)i+(e^15tcost+15e^15tsint)j+( 15te^15t)k

    now i need the norm of r'(t) which i coudn't find

    plz help ??!!
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  2. #2
    Junior Member
    Joined
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    Quote Originally Posted by falta View Post
    hi every one i need help

    Find the unit tangent vector at the indicated point of the vector
    function
    r
    (t) = e^15t cost i+e^15t sint j+e^15t k

    T
    (pi/2) =
    i compute the r'(t) = (-e^15tsint+15e^15tcost)i+(e^15tcost+15e^15tsint)j+( 15te^15t)k

    now i need the norm of r'(t) which i coudn't find

    plz help ??!!
    Forgive me if i'm wrong but isn't the unit tangent vector,  u = \frac{r'(t)}{|r'(t)|} Then let  t = \frac{\pi}{2}
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  3. #3
    MHF Contributor

    Joined
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    Quote Originally Posted by falta View Post
    hi every one i need help

    Find the unit tangent vector at the indicated point of the vector
    function
    r
    (t) = e^15t cost i+e^15t sint j+e^15t k

    T
    (pi/2) =
    i compute the r'(t) = (-e^15tsint+15e^15tcost)i+(e^15tcost+15e^15tsint)j+( 15te^15t)k

    now i need the norm of r'(t) which i coudn't find

    plz help ??!!
    At t= \frac{\pi}{2} sin(t)= 1 and cos(t)= 0. that simplifies everything a lot!

    For example, \vec{r}(t)= e^{15\pi/2}\vec{i}+ e^{15\pi/2}\vec{k}.
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  4. #4
    Newbie
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    Mar 2010
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    thankx .. i got the right answer
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