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

The value of cos(pi)/(5)cos.2(pi)/(5)cos4(pi)/(5)cos8(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(pi)/(8)cos(3 pi)/(8)cos(5 pi)/(8)cos(7 pi)/(8) is equal to

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

Prove that cos((pi)/(8))+cos((3 pi)/(8))+cos((5 pi)/(8))+cos((7 pi)/(8))=0

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

cos ^(2) (3 pi)/(5)+cos ^(2) (4 pi)/(5)=

cos^(2)((3 pi)/(5))+cos^(2)((4 pi)/(5))=