\fLet f(x) = 6 cos x - 9 tan x f' (2 ) =If f(x) = 3 sinx + 7 cos x, then f' (2 ) = f' (2 ) =Find the 50 th derivative of the function f(x) = cos(x). The answer is functionIf f(x) = cos x - 2 tan x, then f' (20 ) =