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

"cos(pi/15)cos((2pi)/15)cos((4pi)/15)cos((8pi)/15)=k

cos(pi/65)cos((2pi)/65)cos((4pi)/65)cos((8pi)/65)cos((16pi)/65)cos((32pi)/64)=1/64

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

cos(pi/11) cos((2pi)/11) cos((3pi)/11)....cos((11pi)/11)=

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 1 (b) -1 (c) 0 (d) none of these

Show that cos(pi/65)cos((2pi)/65)cos((4pi)/65)cos((8pi)/65)cos((16pi)/65)cos((32pi)/65)=1/64

2cos(pi/13)cos(9pi/13)+cos(3pi/13)+cos(5pi/13)=0

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

Prove that cos(2pi)/(15)cos(4pi)/(15)cos(8pi)/(15)cos(14pi)/(15)=1/(16)