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

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

The value of cos(pi)/(5)cos.2(pi)/(5)cos4(pi)/(5)cos8(pi)/(5)=

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

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

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

Prove: cos(pi/15)cos((2pi)/15)cos((3pi)/15)cos((4pi)/15)cos((5pi)/15)cos((6pi)/15)cos((7pi)/15) = 1/2^7

Show that cos(pi/15)cos((2pi)/15)cos((3pi)/15)cos((4pi)/15)cos((5pi)/15)cos((6pi)/15)cos((7pi)/15) = 1/2^7

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

The value of cos((pi)/(7))+cos((2 pi)/(7))+cos((3 pi)/(7))+cos((4 pi)/(7))+cos((5 pi)/(7))+cos((6 pi)/(7))+cos((7 pi)/(7)) is 1(b)-1(c)0(d) none of these