Prove that `(1+cos(pi/10))(1+cos(3pi/10))(1+cos(7pi/10))(1+cos(9pi/10))=1/16`

Prove that (1 + cos(pi/8))(1 + cos(3pi/8))(1 + cos(5pi/8))(1 + cos(7pi/8)) = 1/8

Evaluate: (1+cos(pi/8))(1+cos(3pi/8))(1+cos(5pi/8))(1+cos (7pi/8))

Prove that (1+cos pi/9) (1 + cos 3pi/9) (1+ cos 5pi/9) (1 + cos 7pi/9) =9/16 .

Prove that: (1+cos(pi)/(8))(1+cos(3 pi)/(8))(1+cos(5 pi)/(8))(1+cos(7 pi)/(8))=(1)/(8)

The value oif the expressin (1+(cos pi)/(10))(1+(cos(3 pi))/(10))(1+(cos(7 pi))/(10))(1+(cos(9 pi))/(10)) is

Prove that cos((2pi)/7) cos((4pi)/7) cos((8pi)/7) =1/8

Prove that :16cos2(pi)/(15)cos4(pi)/(15)cos8(pi)/(15)cos16(pi)/(15)=1

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

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