Ok so ##\vec{T}(t)##, ##\vec{N}(t)##, and ##\vec{a}_{v\perp}## arent ever mentioned in any previous problem for this homework, but in the text they are given as:
##\vec{T}(t) = \frac{\vec{v}(t)}{v(t)}## so a unit vector in the direction of the velocity vector.
##\vec{N}(t) =...