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

The value of (1+cos (pi)/(8))(1+cos (3 pi)/(8))(1+cos (5 pi)/(8))(1+cos (7 pi)/(8)) is

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

cos^2 ""(pi)/(8) + cos ^2 ""(3 pi)/(8) + cos ^2 ""(5 pi)/(8) + cos ^2 ""(7 pi)/(8) is

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

Prove that cos ^(4) ""(pi)/(8) + cos ^(4) ""(3pi)/(8) + cos ^(4) ""(5pi)/(8) + cos ^(4) "" (7pi)/(8) = (3)/(2)

((1 + "cos"(pi)/(8) -i "sin"(pi)/(8))/(1 + "cos"(pi)/(8) + i "sin" (pi)/(8)))^(12)=