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

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

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

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

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)

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

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

If A=sin((2 pi)/(7))+sin((4 pi)/(7))+sin((8 pi)/(7)) and B=cos((2 pi)/(7))+cos((4 pi)/(7))+cos((8 pi)/(7)) then sqrt(A^(2)+B^(2)) is equal to