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?
For (a), just multiply the two functions together:
For (b), divide the two functions together (which is the same as multiplying by the reciprocal):
For (c), in f(x), plug in g(x) for x:
For (d), in g(x), plug in f(x) for x:
I hope that you don't have to simplify these.