cos(pi)/(5)-cos(2 pi)/(5)

Prove that, cos(pi/5)-cos((2pi)/5)=1/2

cos((pi)/(15))cos((2 pi)/(15))cos((pi)/(5))cos((4 pi)/(15))cos((2 pi)/(5))cos((7 pi)/(15)) is equal to

Find the value of cos((2pi)/5).cos(pi/5)

cos(pi/5)cos((2pi)/5)cos((4pi)/5)cos((8pi)/5)=

Prove that: cos(pi/5)cos((2pi)/5)cos((4pi)/5)cos((8pi)/5)=(-1)/16

The value of cos[(1)/(2)cos^(-1)(cos(-(14 pi)/(5)))] is/are a.cos (-(7 pi)/(5)) b.sin((pi)/(10))ccos((2 pi)/(5))d.-cos((3 pi)/(5))

The value of cos((pi)/(5))+cos((13 pi)/(5)) is equal to

let x_(1)=cos((pi)/(11))cos((2 pi)/(11))cos((3 pi)/(11))cos((4 pi)/(11))cos((5 pi)/(11)) and x_(2)=cos((pi)/(11))+cos(2(pi)/(11))+cos(3(pi)/(11))+cos(4(pi)/(11))+cos(5(pi)/(11)) then show that x_(1).x_(2)=(1)/(64)(cos ec((pi)/(22))-1)

The value of cos""(pi)/(7)+cos""(2pi)/(7)cos""(3pi)/(7)+cos""(4pi)/(7)+cos""(5pi)/(7)+cos""(6pi)/(7)+cos""(7pi)/(7) is