Where is my mistake?

Find the unit tangent vector at (1,2/3,1) => t=1.

r(t)=<t^2,(2/3)t^3,t>

r'(t)=<2t,2*t^2,1>
|r'(t)|=SQRT(4*t^2+4*t^4+1)

T(t)=<2t,2*t^2,1>/(SQRT(4*t^2+4*t^4+1))

T(1)=<2,2,1>/(SQRT(9))=<2/3,2/3,1/3>

But the back of the book says <2/3,2/3,1/3>. Nevermind, I need some remedial reading classes.

[Edited on July 9, 2007 at 6:52 PM. Reason : derivative]

7/9/2007 6:47:56 PM

np

7/9/2007 8:21:40 PM

^^the same thing happens IRL all the time, here TWW itself has answered the problem, interesting.

7/9/2007 9:09:42 PM