Find (f^-1)' (a) for each function f and real number a.

(1) f(x) = sqrt(x-4) when a = 2.

(2) f(x) = cos(2x), Where 0 is less than or equal to x less than or equal to (pi/2). For question 2, a = 1.

I would like only the steps for each question. Thank you.