ling 111 introduction to english vocabulary analysis

please teach me the following method.i think for 2,3 we need use dictionary. but i don’t know how.

1. how to determine whether a pair of words are cognate or not? e.g.1, father – paternal ans: yes etc.

2. how to find the native english cognate if a Latin or Greek borrowings were given? E.G. farina — ans:barn, barley,

3.how to find Latin cognates if an English word is given.