Solution:

(i) E = The set of all letters in the word TRIGONOMETRY

TRIGONOMETRY is a 12 letters word out of which T, R and O are repeated.

As a result, the provided set can be written in the roster form as

E = {T, R, I, G, O, N, M, E, Y}

(ii) F = In the word BETTER the set of all letters.

BETTER is a six letter word out of which the letters E and T are repeated.

As a result, the provided set can be written in the roster form as

F = {B, E, T, R}