" 19The value of "cos(pi)/(5)cos(2 pi)/(5)cos(4 pi)/(5)cos(8 pi)/(5)" is "

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)=

The value of cos(pi)/(8)cos(3 pi)/(8)cos(5 pi)/(8)cos(7 pi)/(8) is equal to

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

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

The value of (cos pi)/(11)+(cos(3 pi))/(11)+(cos(5 pi))/(11)+(cos(7 pi))/(11)+(cos(9 pi))/(11)

Prove that: (cos pi)/(5)(cos(2 pi))/(5)(cos(4 pi))/(5)(cos(8 pi))/(5)=(-1)/(6)

The value of cos((pi)/(19))+cos((3 pi)/(19))+cos((5 pi)/(19))++cos((17 pi)/(19)) is (a) (1)/(2)(b)0(c)1 (d)none