To find (a) and (b), use the difinitions of cscx=1/sinx and tanx=sinx/cosx.

For (c) and (d) first clarify which f and g do you mean and then use definition of composition of functions (f∘g)(x)=f(g(x)) and subsituate g(x) instead of x in f. Similar for g∘f.

Domain and range for which ones?