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Question Number 31035 by abdo imad last updated on 02/Mar/18

1) s o l v e x^{5} = 1

2) i f x_{i} a r e r o o t s o f t h i s e q u a t i o n p r o v e t h a t \sum_{i} x_{i} = 0

3) p r o v e t h a t c o s (\frac{2 π}{5}) + c o s (\frac{4 π}{5}) = - \frac{1}{2}

4) c a l c u l a t e c o s (\frac{4 π}{5}) i n t e r m s c o s (\frac{2 π}{5}) t h e n f i n d i t s

v a l u e s .