`Cos ((2pi)/7) + Cos ((4pi)/7) + cos ((6pi)/7) = -1/2`

Prove that cos((2pi)/7) cos((4pi)/7) cos((8pi)/7) =1/8

Prove that cos((2pi)/7)cos((4pi)/7)cos((8pi)/7)=1/8

cos ((pi) / (7)) cos ((2 pi) / (7)) cos ((4 pi) / (7)) =

cos ((pi) / (7)) * cos ((2 pi) / (7)) * cos ((3 pi) / (7)) =

The numerical value of cos(( pi)/15)* cos ((2pi)/15)* cos ((4pi)/15) cos ((7pi)/15) = ...........

cos (2 (pi) / (7)) cos (4 (pi) / (7)) * cos (6 (pi) / (7))

1+cos((2 pi)/(7))+cos((4 pi)/(7))+cos((6 pi)/(7)) is equal to (i)-(1)/(2)(ii)0( iii) (1)/(2)(iv)(3)/(2)

If the value of cos((2 pi)/(7))+cos((4 pi)/(7))+cos((6 pi)/(7))+cos((7(pi)/(7)))=-(l)/(2) Find the value of l

(cos pi) / (5) + (cos (2 pi)) / (5) + (cos (6 pi)) / (5) + (cos (7 pi)) / (5) = 0