cant undertstand

8 The sum to infinity of a geometric series is 96 The first term of the series is less than 30 The second term of the series is 18 8 (a) Find the first term and common ratio of the series. [5 marks] 8 (b) (i) Show that the nth term of the series, u,, can be written as Un 22n-5 [4 marks] 8 (b) (ii) Hence show that log3 Un = n(1 - 21093 2) + 5log3 2 [3 marks] 9 (a) For cos 0 # 0, prove that cosec 20 + cot 20 = cot 0 [4 marks] 9 (b) Explain why cot 0 # cosec 20 + cot 20 when cos 0 = 0 [1 mark]