I get about halfway through this question then I get stuck on positive and negative values, Can I ask that as much detail as possible be included so I can understand what I'm doing wrong?

Write a in the form a=a_tT+a_NN at the given value of t without finding T and N. r(t)=(e^tcost)i+(e^tsqrt(5))j+(e^tsint)k, t=0

Write a in the form a = a T + ayN at the given value of t without finding T and N. r(t) = (ecos t)i+ (ev5)j+ (esin t)k, t=0 a(0) = ()T+ N (Type exact answers, using radicals as needed.)