Q.:A geometric series has first term 1 and common ratio 1/2sin2(theta).

(i) Find the sum of the first 10 terms when theta = pi/ 4, giving your answer in the form h - 1/2^k, where h, k E (i.e is a set of) N.

(ii) Given that the sum to infinty is 4/3, find the value of theta if theta < 90 degrees.

NB:I've already solved part (i), the jpg shows my attempt at part (ii).

Ans.:From text book: 15 degrees.

Thank you.