`Cos^2(pi/8) + cos^2((3pi)/8) + cos^2((5pi)/8) + cos^2((7pi)/8) = 2`

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

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

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

Prove that cos((pi)/(8))+cos((3 pi)/(8))+cos((5 pi)/(8))+cos((7 pi)/(8))=0

Statement I : sin^2pi/8+sin^2(3pi)/8+sin^2(5pi)/8+sin^2(7pi)/8=2 Statement II cos^2pi/8+cos^2(3pi )/8+cos^2(5pi)/8+cos^2(7pi/8)=2 Statement III: sin^2pi/8+sin^(3pi)/8+sin^2(5pi)/8sin^2 (7pi)/8=3/2

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

The value of sin^(4)(pi/8)+cos^(4)((3 pi)/8)+sin^(4)((5pi)/8)+cos^(4)((7pi)/8) is equal to =