Prove that: `sin^(2)(pi)/(8)+sin^(2)(3 pi)/(8)+sin^(2)(5 pi)/(8)+sin^(2)(7 pi)/(8)=2`

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

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

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

Prove that: sin^2pi/(18)+sin^2pi/9+sin^2(7pi)/(18)+sin^2(4pi)/9=2

Prove that: sin^2pi/(18)+sin^2pi/9+sin^2(7pi)/(18)+sin^2(4pi)/9=2

Prove that: sin ((pi)/(7))+sin((2pi)/(7)) + sin((8pi)/(7)) + sin((9pi)/(7))=0

Prove that: 2sin^(2)((pi)/(6))+cosec^(2)((7 pi)/(6))cos^(2)((pi)/(3))=(3)/(2)

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

Prove that: sin(pi/10)+sin((13pi)/10)=-1/2

sin ^(4) "" (pi)/(8) + sin ^(4) "" (3pi)/(8) + sin ^(4) "" (5pi)/(8) + sin ^(4)"" (7pi)/(8) = (3)/(2).