How to do this question i don't understand it

Which function is odd check all that apply a. y=sin x b. y=csc x c. y=cot x d. y=sec x

X/y + 4y/x divided by x/y - 2y/x explain as in depth as you can how you simplfied the fractions. i don't know where to start on this : /

Determine which postulate or theorem can be used to prove that lmn =nmo