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

cos""(2pi)/(15)cos""(4pi)/(15)cos""(8pi)/(15)cos""(16pi)/(15)=(1)/(16)

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

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

Prove that: 8(cos^(3)pi)/(9)-6(cos pi)/(9)=1

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

"cos"^(-1)("cos"((7pi)/(5)))=

Prove that :(cos pi)/(7)(cos(2 pi))/(7)(cos(3 pi))/(7)(cos(4 pi))/(7)=(1)/(8)