Gunakan Konsep limit untuk menentukan turunan fungsi dari f(x) =cos (1-3x)......Please

f'(x) = lim h~0 [f(x+h) - f(x)]/h
= lim h~0 [cos(1-3(x+h))-cos(1-3x)]/h
= lim h~0 [cos(1-3x-3h)-cos(1-3x)]/h
= lim h~0 [-2 sin (1/2(2-6x-3h) sin(1/2(-3h))/h
= lim h~0 [-2.-3/2 sin (1-3x-3/2h)sin(-3/2h)]/-3/2h
= lim h~0 (-3 sin(1-3x-3/2h)(sin(-3/2h)/(-3/2h)
= lim h~0 (-3 sin (1-3x-3/2h).1
= -3 sin(1-3x-3/2(0))
= -3 sin(1-3x)