Thank you in advance

Question 8 Find f' (z) for f (3) = 1 - cos I Of ( =) = COS I - COS 23 (1 - cos z)2 Of ( z) = -1 1 - cos I P f (z) - COBI- EIn Of ( I ) COS 2 - 1 cost COS Z Of ( =) = (1 COS )2