Find the value of `cos^(4)""(pi)/(8)+cos^(4)""(3pi)/(8)+cos^(4)""(5pi)/(8)+cos^(4)""(7pi)/(8)`.

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

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

Find the values of cos pi/8

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

Find cos "" (7pi)/(8).

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

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

Evaluate : 8 cos ^(3) ""(pi)/(9)- 6cos ""(pi)/(9)

Find the value of cos""(pi)/(12)(sin""(5pi)/(12)+cos""(pi)/(4))+sin""(pi)/(12)(cos""(5pi)/(12)-sin""(pi)/(4)) .

Find the value of 2cos^3(pi/7)-cos^2(pi/7)-cos(pi/7)