" 12.Prove that "(1+cos(pi)/(10))(1+cos(3 pi)/(10))(1+cos(7 pi)/(10))(1+cos(9 pi)/(10))=(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/10))(1+cos(3pi/10))(1+cos(7pi/10))(1+cos(9pi/10))=1/16

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

The value of cos((pi)/(10))cos((2 pi)/(10))cos((4 pi)/(10))cos((8 pi)/(10))cos((16 pi)/(10))

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

cos(pi)/(11)+cos(3 pi)/(11)+cos(5 pi)/(11)+cos(7 pi)/(11)+cos(9 pi)/(11)=(1)/(2)

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

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